Relationship between dissolved organic carbon and bacterial community in the coastal waters of Incheon, Korea

Azam, F. & Malfatti, F. (2007). Microbial structuring of marine ecosystems. Nat Rev Micro 5(10): 782-791. DOI: 10.1038/ nrmicro1747.AzamFMalfattiF2007Microbial structuring of marine ecosystemsNat Rev Micro51078279110.1038/ nrmicro1747Open DOISearch in Google Scholar

Buchan, A., LeCleir, G.R., Gulvik, C.A. & González, J.M. (2014). Master recyclers: features and functions of bacteria associated with phytoplankton blooms. Nat. Rev. Microbiol. 12(10): 686-698. DOI: 10.1038/nrmicro3326.BuchanALeCleirG.RGulvikC.AGonzálezJ.M2014Master recyclers: features and functions of bacteria associated with phytoplankton bloomsNat. Rev. Microbiol121068669810.1038/nrmicro332625134618Open DOISearch in Google Scholar

Campbell, B.J. & Kirchman, D.L. (2013). Bacterial diversity, community structure and potential growth rates along an estuarine salinity gradient. The ISME journal 7(1): 210-220. DOI: 10.1038/ismej.2012.93.CampbellB.JKirchmanD.L2013Bacterial diversity, community structure and potential growth rates along an estuarine salinity gradientThe ISME journal7121022010.1038/ismej.2012.93352618122895159Open DOISearch in Google Scholar

Chen, B., Wang, J., Tang, J. & Wen, S. (2002). Prediction to trend of nutrient status in Meizhou Bay, Fujian. Mar. Biol. J. Oceanogr. in Taiwan Strait/Taiwan Haixia. Xiamen 21(3): 322-327ChenBWangJTangJWenS2002Prediction to trend of nutrient status in Meizhou Bay, FujianMar. Biol. J. Oceanogr. in Taiwan Strait/Taiwan Haixia. Xiamen213322327Search in Google Scholar

Cotter, P.D. & Hill, C. (2003). Surviving the acid test: responses of gram-positive bacteria to low pH. Microbiol. Mol. Biol. Rev. 67(3): 429-453. DOI: 10.1128/MMBR.67.3.429-453.2003.CotterP.DHillC2003Surviving the acid test: responses of gram-positive bacteria to low pHMicrobiol. Mol. Biol. Rev67342945310.1128/MMBR.67.3.429-453.200319386812966143Open DOISearch in Google Scholar

Crump, B.C., Kling, G.W., Bahr, M. & Hobbie, J.E. (2003). Bacterioplankton community shifts in an arctic lake correlate with seasonal changes in organic matter source. Appl. Environ. Microbiol. 69(4): 2253-2268. DOI: 10.1128/ AEM.69.4.2253-2268.2003.CrumpB.CKlingG.WBahrMHobbieJ.E2003Bacterioplankton community shifts in an arctic lake correlate with seasonal changes in organic matter sourceAppl. Environ. Microbiol6942253226810.1128/ AEM.69.4.2253-2268.2003Open DOISearch in Google Scholar

Del Giorgio, P.A. & Cole, J.J. (1998). Bacterial growth efficiency in natural aquatic systems. Annu. Rev. Ecol. Syst. 503-541.Del GiorgioP.AColeJ.J1998Bacterial growth efficiency in natural aquatic systemsAnnu. Rev. Ecol. Syst50354110.1146/annurev.ecolsys.29.1.503Search in Google Scholar

Dubois, J., Hill, S., England, L, Edge, T., Masson, L et al. (2004). The development of a DNA microarray-based assay for the characterization of commercially formulated microbial products. J. Microbiol. Methods 58(2): 251-262. DOI: 10.1016/j.mimet.2004.04.011.DuboisJHillSEnglandLEdgeTMassonL2004The development of a DNA microarray-based assay for the characterization of commercially formulated microbial productsJ. Microbiol. Methods58225126210.1016/j.mimet.2004.04.01115234523Open DOISearch in Google Scholar

Ederington, M.C., McManus, G.B. & Harvey, H.R. (1995). Trophic transfer of fatty acids, sterols, and a triterpenoid alcohol between bacteria, a ciliate, and the copepod Acartia tonsa. Limnol. Oceanogr. 40(5): 860-867. DOI: 10.4319/ lo.1995.40.5.0860.EderingtonM.CMcManusG.BHarveyH.R1995Trophic transfer of fatty acids, sterols, and a triterpenoid alcohol between bacteria, a ciliate, and the copepodAcartia tonsa. Limnol. Oceanogr40586086710.4319/ lo.1995.40.5.0860Open DOISearch in Google Scholar

Eiler, A., Langenheder, S., Bertilsson, S. & Tranvik, L.J. (2003). Heterotrophic bacterial growth efficiency and community structure at different natural organic carbon concentrations. Appl. Environ. Microbiol. 69(7): 3701-3709. DOI: 10.1128/AEM.69.7.3701-3709.2003.EilerALangenhederSBertilssonSTranvikL.J2003Heterotrophic bacterial growth efficiency and community structure at different natural organic carbon concentrationsAppl. Environ. Microbiol6973701370910.1128/AEM.69.7.3701-3709.200316518412839735Open DOISearch in Google Scholar

Elser, J.J., Stabler, L.B. & Hassett, R.P. (1995). Nutrient limitation of bacterial growth and rates of bacterivory in lakes and oceans: a comparative study. Aquat. Microb. Ecol. 9(2): 105-110. DOI: 10.3354/ame009105.ElserJ.JStablerL.BHassettR.P1995Nutrient limitation of bacterial growth and rates of bacterivory in lakes and oceans: a comparative studyAquat. Microb. Ecol9210511010.3354/ame009105Open DOISearch in Google Scholar

Falkowski, P.G. & Raven, J.A. (2007). Aquatic photosynthesis: Princeton University Press.FalkowskiP.GRavenJ.A2007Aquatic photosynthesisPrinceton University Press10.1515/9781400849727Search in Google Scholar

Ferrari, V. & Hollibaugh, J. (1999). Distribution of microbial assemblages in the Central Arctic Ocean Basin studied by PCR/DGGE: analysis of a large data set. Hydrobiologia 401: 55-68. DOI: 10.1023/A:1003773907789.FerrariVHollibaughJ1999Distribution of microbial assemblages in the Central Arctic Ocean Basin studied by PCR/DGGE: analysis of a large data setHydrobiologia401556810.1023/A:1003773907789Open DOISearch in Google Scholar

Findlay, S.E. (2005). Increased carbon transport in the Hudson River: unexpected consequence of nitrogen deposition? Front. Ecol. Environ. 3(3): 133-137. DOI: 10.1890/1540-9295(2005)003[0133:ICTITH]2.0.CO;2.FindlayS.E2005Increased carbon transport in the Hudson River: unexpected consequence of nitrogen deposition?Front. Ecol. Environ3313313710.1890/1540-9295(2005)003[0133:ICTITH]2.0.CO;2Open DOISearch in Google Scholar

Freeman, C, Evans, C, Monteith, D., Reynolds, B. & Fenner, N. (2001). Export of organic carbon from peat soils. Nature 412(6849): 785-785. DOI: 10.1038/35090628.FreemanCEvansCMonteithDReynoldsBFennerN2001Export of organic carbon from peat soilsNature412684978578510.1038/35090628Open DOISearch in Google Scholar

Freeman, C, Fenner, N., Ostle, N., Kang, H., Dowrick, D. et al. (2004). Export of dissolved organic carbon from peatlands under elevated carbon dioxide levels. Nature 430(6996): 195-198. DOI: 10.1038/nature02707.FreemanCFennerNOstleNKangHDowrickD2004Export of dissolved organic carbon from peatlands under elevated carbon dioxide levelsNature430699619519810.1038/nature02707Open DOISearch in Google Scholar

Fuhrman J. (1992). Bacterioplankton roles in cycling of organic matter: the microbial food web. In Primary productivity and biogeochemical cycles in the sea. Springer.FuhrmanJ1992Bacterioplankton roles in cycling of organic matter: the microbial food webIn Primary productivity and biogeochemical cycles in the seaSpringer10.1007/978-1-4899-0762-2_20Search in Google Scholar

Garnett, M., Ineson, P. & Stevenson, A. (2000). Effects of burning and grazing on carbon sequestration in a Pennine blanket bog, UK. The Holocene 10(6): 729-736. DOI: 10.1191/09596830094971.GarnettMInesonPStevensonA2000Effects of burning and grazing on carbon sequestration in a Pennine blanket bog, UKThe Holocene10672973610.1191/09596830094971Open DOISearch in Google Scholar

Gonzalez, J.M., Sherr, E.B. & Sherr, B.F. (1990). Size-selective grazing on bacteria by natural assemblages of estuarine flagellates and ciliates. Appl. Environ. Microbiol. 56(3): 583-589.GonzalezJ.MSherrE.BSherrB.F1990Size-selective grazing on bacteria by natural assemblages of estuarine flagellates and ciliatesAppl. Environ. Microbiol56358358910.1128/aem.56.3.583-589.1990Search in Google Scholar

Kirchman, D. (1994). The uptake of inorganic nutrients by heterotrophic bacteria. Microb. Ecol. 28(2): 255-271. DOI: 10.1007/BF00166816.KirchmanD1994The uptake of inorganic nutrients by heterotrophic bacteriaMicrob. Ecol28225527110.1007/BF00166816Open DOISearch in Google Scholar

Kjelleberg, S. (1993). Starvation in bacteria. Springer.KjellebergS1993Starvation in bacteriaSpringer10.1007/978-1-4899-2439-1Search in Google Scholar

Kuuppo-Leinikki, P. (1990). Protozoan grazing on planktonic bacteria and its impact on bacterial population. Mar. Ecol. Prog. Ser. 63(2): 227-238.Kuuppo-LeinikkiP1990Protozoan grazing on planktonic bacteria and its impact on bacterial populationMar. Ecol. Prog. Ser63222723810.3354/meps063227Search in Google Scholar

Larsson, U. & Hagström, A. (1979). Phytoplankton exudate release as an energy source for the growth of pelagic bacteria. Mar. Biol. 52(3): 199-206. DOI: 10.1007/ BF00398133.LarssonUHagströmA1979Phytoplankton exudate release as an energy source for the growth of pelagic bacteriaMar. Biol52319920610.1007/ BF00398133Open DOISearch in Google Scholar

Maas, E.W., Law, CS., Hall, J.A., Pickmere, S., Currie, K.I. et al. (2013). Effect of ocean acidification on bacterial abundance, activity and diversity in the Ross Sea, Antarctica. Aquat Microb. Ecol. 70(1): 1-15. DOI: 10.3354/ ame01633.MaasE.WLawC.SHallJ.APickmereSCurrieK.I2013Effect of ocean acidification on bacterial abundance, activity and diversity in the Ross Sea, AntarcticaAquat Microb. Ecol70111510.3354/ame01633Open DOISearch in Google Scholar

Morrow, K., Paul, V., Liles, M. & Chadwick, N. (2011). Allelochemicals produced by Caribbean macroalgae and cyanobacteria have species-specific effects on reef coral microorganisms. Coral Reefs 30(2): 309-320. DOI: 10.1007/ s00338-011-0747-1.MorrowKPaulVLilesMChadwickN2011Allelochemicals produced by Caribbean macroalgae and cyanobacteria have species-specific effects on reef coral microorganismsCoral Reefs30230932010.1007/ s00338-011-0747-1Open DOISearch in Google Scholar

Muyzer, G., Teske, A., Wirsen, CO. & Jannasch, H.W. (1995). Phylogenetic relationships of Thiomicrospira species and their identification in deep-sea hydrothermal vent samples by denaturing gradient gel electrophoresis of 16S rDNA fragments. Arch. Microbiol. 164(3): 165-172. DOI: 10.1007/BF02529967.MuyzerGTeskeAWirsenC.OJannaschH.W1995Phylogenetic relationships of Thiomicrospira species and their identification in deep-sea hydrothermal vent samples by denaturing gradient gel electrophoresis of 16S rDNA fragmentsArch. Microbiol164316517210.1007/BF025299677545384Open DOISearch in Google Scholar

Nester, E.W. (2001). Microbiology: a human perspective. McGraw-Hill.NesterE.W2001Microbiology: a human perspectiveMcGraw-HillSearch in Google Scholar

Ogawa, H. & Tanoue, E. (2003). Dissolved organic matter in oceanic waters. J. Oceanogr. 59(2): 129-147. DOI: 10.1023/A:1025528919771.OgawaHTanoueE2003Dissolved organic matter in oceanic watersJ. Oceanogr59212914710.1023/A:1025528919771Open DOISearch in Google Scholar

Park, B.S., Wang, P., Kim, J.H., Kim, J.-H., Gobler, C.J. et al. (2014). Resolving the intra-specific succession within Cochlodinium polykrikoides populations in southern Korean coastal waters via use of quantitative PCR assays. Harmful Algae 37: 133-141. DOI: 10.1016/j.hal.2014.04.019.ParkB.SWangPKimJ.HKimJ-H.GoblerC.J2014Resolving the intra-specific succession within Cochlodinium polykrikoides populations in southern Korean coastal waters via use of quantitative PCR assaysHarmful Algae3713314110.1016/j.hal.2014.04.019Open DOISearch in Google Scholar

Park, N., Kim, J.H. & Cho, J. (2008). Organic matter, anion, and metal wastewater treatment in Damyang surface-flow constructed wetlands in Korea. Ecol. Eng. 32(1): 68-71.ParkNKimJ.HChoJ2008Organic matter, anion, and metal wastewater treatment in Damyang surface-flow constructed wetlands in KoreaEcol. Eng321687110.1016/j.ecoleng.2007.09.003Search in Google Scholar

Park, S., Park, G., Seok, K., Oh, H., Lee, Y. et al. (1999). Spatio temporal variation of water quality and eutrophication in the Kyunggi Bay of Yellow Sea, Korea. Bull. Nat. 1: 189-204.ParkSParkGSeokKOhHLeeY1999Spatio temporal variation of water quality and eutrophication in the Kyunggi Bay of Yellow Sea, KoreaBull. Nat1189204Search in Google Scholar

Pomeroy, L.R. & Wiebe, W.J. (2001). Temperature and substrates as interactive limiting factors for marine heterotrophic bacteria. Aquat. Microb. Ecol. 23(2): 187-204. DOI: 10.3354/ ame023187.PomeroyL.RWiebeW.J2001Temperature and substrates as interactive limiting factors for marine heterotrophic bacteriaAquat. Microb. Ecol23218720410.3354/ ame023187Open DOISearch in Google Scholar

Porter, K. & Feig, Y (1980). The use of DAPI for identification and enumeration of bacteria and blue-green algae. Limnol. Oceanogr. 25: 943-948.PorterKFeigY1980The use of DAPI for identification and enumeration of bacteria and blue-green algaeLimnol. Oceanogr2594394810.4319/lo.1980.25.5.0943Search in Google Scholar

Ratkowsky, D., Olley, J., McMeekin, T. & Ball, A. (1982). Relationship between temperature and growth rate of bacterial cultures. J. Bacteriol. 149(1): 1-5.RatkowskyDOlleyJMcMeekinTBallA1982Relationship between temperature and growth rate of bacterial culturesJ. Bacteriol14911510.1128/jb.149.1.1-5.1982Search in Google Scholar

Redfield, AC. (1958). The biological control of chemical factors in the environment. Am. Sci. 205-221.RedfieldA.C1958The biological control of chemical factors in the environmentAm. Sci20522110.1515/9783112312308-007Search in Google Scholar

Roh, S.W., Abell, G.C, Kim, K.-H., Nam, Y.-D. & Bae, J.-W. (2010). Comparing microarrays and next-generation sequencing technologies for microbial ecology research. Trends Biotechnol. 28(6): 291-299. DOI: 10.1016/j.tibtech.2010.03.001.RohS.WAbellG.CKimK.-H.NamY.-D.BaeJ.-W.2010Comparing microarrays and next-generation sequencing technologies for microbial ecology researchTrends Biotechnol28629129910.1016/j.tibtech.2010.03.001Open DOISearch in Google Scholar

Samarajeewa, A., Hammad, A., Masson, L., Khan, I., Scroggins, R. et al. (2015). Comparative assessment of next-generation sequencing, denaturing gradient gel electrophoresis, clonal restriction fragment length polymorphism and cloning-sequencing as methods for characterizing commercial microbial consortia. J. Microbiol. Methods 108: 103-111. DOI: 10.1016/j.mimet.2014.11.013.SamarajeewaAHammadAMassonLKhanIScrogginsR2015Comparative assessment of next-generation sequencing, denaturing gradient gel electrophoresis, clonal restriction fragment length polymorphism and cloning-sequencing as methods for characterizing commercial microbial consortiaJ. Microbiol. Methods10810311110.1016/j.mimet.2014.11.013Open DOISearch in Google Scholar

Schimel, D.S. (1995). Terrestrial ecosystems and the carbon cycle. Global Change Biol. 1(1): 77-91. DOI: 10.1111/j.1365- 2486.1995.tb00008.x.SchimelD.S1995Terrestrial ecosystems and the carbon cycleGlobal Change Biol11779110.1111/j.1365- 2486.1995.tb00008.xOpen DOISearch in Google Scholar

Schneider, B. & Schmittner, A. (2006). Simulating the impact of the Panamanian seaway closure on ocean circulation, marine productivity and nutrient cycling. Earth Planet Sci. Lett. 246(3), 367-380. DOI: 10.1016/j.epsl.2006.04.028.SchneiderBSchmittnerA2006Simulating the impact of the Panamanian seaway closure on ocean circulation, marine productivity and nutrient cyclingEarth Planet Sci.Lett246336738010.1016/j.epsl.2006.04.028Open DOISearch in Google Scholar

Smith, J.E., Shaw, M., Edwards, R.A., Obura, D., Pantos, O. et al. (2006). Indirect effects of algae on coral: algae-mediated, microbe-induced coral mortality. Ecol. Lett. 9(7): 835-845. DOI: 10.1111/j.1461-0248.2006.00937.x.SmithJ.EShawMEdwardsR.AOburaDPantosO2006Indirect effects of algae on coral: algae-mediated, microbe-induced coral mortalityEcol. Lett9783584510.1111/j.1461-0248.2006.00937.xOpen DOISearch in Google Scholar

Smith, R., Gosselin, M., Kudoh, S., Robineau, B. & Taguchi, S. (1997). DOC and its relationship to algae in bottom ice communities. J. Mar. Syst. 11(1): 71-80. DOI: 10.1016/ S0924-7963(96)00029-2.SmithRGosselinMKudohSRobineauBTaguchiS1997DOC and its relationship to algae in bottom ice communitiesJ. Mar. Syst111718010.1016/ S0924-7963(96)00029-2Open DOISearch in Google Scholar

Song, M.-Y., Sohn, M.-H., Im, Y.-J., Kim, J.-B., Kim, H.-Y. et al. (2008). Seasonal variation in the species composition of bag-net catch from the coastal waters of incheon, Korea. Korean Journal of Fisheries and Aquatic Sciences 41(4): 272- 281. DOI: 10.5657/kfas.2008.41.4.272.SongM.-Y.SohnM.-H.ImY.-J.KimJ.-B.KimH.-Y.2008Seasonal variation in the species composition of bag-net catch from the coastal waters of incheon, KoreaKorean Journal of Fisheries and Aquatic Sciences41427228110.5657/kfas.2008.41.4.272Open DOISearch in Google Scholar

Strickland, J.D.H. & Parsons, T.R. (1972). A practical handbook of seawater analysis. Ottawa, Canada: Fisheries Research Board of Canada.StricklandJ.D.H.ParsonsT.R1972A practical handbook of seawater analysisOttawa, CanadaFisheries Research Board of CanadaSearch in Google Scholar

Sundh, I. (1992). Biochemical composition of dissolved organic carbon derived from phytoplankton and used by heterotrophic bacteria. Appl. Environ. Microbiol. 58(9): 2938-2947.SundhI1992Biochemical composition of dissolved organic carbon derived from phytoplankton and used by heterotrophic bacteriaAppl. Environ. Microbiol5892938294710.1128/aem.58.9.2938-2947.199218303016348767Search in Google Scholar

Thornton, DC (2014). Dissolved organic matter (DOM) release by phytoplankton in the contemporary and future ocean. Eur. J. Phycol. 49(1): 20-46. DOI: 10.1080/09670262.2013.875596.ThorntonDC2014Dissolved organic matter (DOM) release by phytoplankton in the contemporary and future oceanEur. J. Phycol491204610.1080/09670262.2013.875596Open DOISearch in Google Scholar

Tsai, A.Y, Gong, G.-C & Huang, Y.W. (2013). Variations of microbial loop carbon flux in western subtropical Pacific coastal water between warm and cold season. J. Exp. Mar. Biol. Ecol. 449, 111-117. DOI: 10.1016/j.jembe.2013.09.006.TsaiA.YGongG.-CHuangY.W2013Variations of microbial loop carbon flux in western subtropical Pacific coastal water between warm and cold seasonJ. Exp. Mar.Biol. Ecol44911111710.1016/j.jembe.2013.09.006Open DOISearch in Google Scholar

Tyrrell, T. (1999). The relative influences of nitrogen and phosphorus on oceanic primary production. Nature 400(6744): 525-531. DOI: 10.1038/22941.TyrrellT1999The relative influences of nitrogen and phosphorus on oceanic primary productionNature400674452553110.1038/22941Open DOISearch in Google Scholar

Verity, P. & Smetacek, V. (1996). Organism life cycles, predation, and the structure of marine pelagic ecosystems. Mar. Ecol. Prog. Ser. 130: 277-293.VerityPSmetacekV1996Organism life cycles, predation, and the structure of marine pelagic ecosystemsMar. Ecol.Prog. Ser13027729310.3354/meps130277Search in Google Scholar

Wang, H., Hill, R.T., Zheng, T., Hu, X. & Wang, B. (2016). Effects of bacterial communities on biofuel-producing microalgae: stimulation, inhibition and harvesting. Crit. Rev. Biotechnol. 36(2): 341-352. DOI: 10.3109/07388551.2014.961402.WangHHillR.TZhengTHuXWangB2016Effects of bacterial communities on biofuel-producing microalgae: stimulation, inhibition and harvestingCrit. Rev. Biotechnol36234135210.3109/07388551.2014.961402Open DOISearch in Google Scholar

Wang, P., Park, B.S., Kim, J.H., Kim, J.-H., Lee, H.-O. et al. (2014). Phylogenetic position of eight Amphora sensu lato (Bacillariophyceae) species and comparative analysis of morphological characteristics. Algae 29(2): 57-73. DOI: 10.4490/algae.2014.29.2.057.WangPParkB.SKimJ.HKimJ.-H.LeeH.-O.2014Phylogenetic position of eight Amphora sensu lato (Bacillariophyceae) species and comparative analysis of morphological characteristicsAlgae292577310.4490/algae.2014.29.2.057Open DOISearch in Google Scholar

Watanabe, T., Asakawa, S., Nakamura, A., Nagaoka, K. & Kimura, M. (2004). DGGE method for analyzing 16S rDNA of methanogenic archaeal community in paddy field soil. FEMS Microbiol. Lett. 232(2): 153-163. DOI: 10.1016/S0378- 1097(04)00045-X.WatanabeTAsakawaSNakamuraANagaokaK.KimuraM2004DGGE method for analyzing 16S rDNA of methanogenic archaeal community in paddy field soilFEMS Microbiol. Lett232215316310.1016/S0378- 1097(04)00045-XOpen DOISearch in Google Scholar

Whitman, W.B., Coleman, D.C. & Wiebe, W.J. (1998). Prokaryotes: the unseen majority. PNAS 95(12): 6578-6583.WhitmanW.BColemanD.CWiebeW.J1998Prokaryotes: the unseen majorityPNAS95126578658310.1073/pnas.95.12.6578338639618454Search in Google Scholar

Worrall, F., Burt, T. & Shedden, R. (2003). Long term records of riverine dissolved organic matter. Biogeochemistry 64(2): 165-178.WorrallFBurtTSheddenR2003Long term records of riverine dissolved organic matterBiogeochemistry64216517810.1023/A:1024924216148Search in Google Scholar

Yoo, J.S. (2008). Productivity and abundance of bacteria and phytoplankton in Incheon Dock, western coast of Korea. J. Environ. Biol. 29: 531-534.YooJ.S2008Productivity and abundance of bacteria and phytoplankton in Incheon Dock, western coast of KoreaJ.Environ. Biol29531534Search in Google Scholar

Yoon, B.I. & Woo, S.-B. (2013). Correlation between freshwater discharge and salinity intrusion in the Han River Estuary, South Korea. J. Coast. Res. 2(65): 1247. DOI: 10.2112/SI65- 211.1.YoonB.IWooS.-B.2013Correlation between freshwater discharge and salinity intrusion in the Han River Estuary, South KoreaJ. Coast. Res265124710.2112/SI65- 211.1Open DOISearch in Google Scholar