[1. http://osfm.fire.ca.gov/pipeline/pdf/conferece/inlineinspection.pdf,]Search in Google Scholar
[2. http://www.peg-germany.de/en/products/pipeline-products/pipeline-spheres.html,]Search in Google Scholar
[3. Rowiński L.: Deep-water vehicles: structure and equipment (in Polish), WiB Gdansk 2008,]Search in Google Scholar
[4. http://www.inlineservices.com/pipeline-pig-brushes,]Search in Google Scholar
[5. https://deutsch.rt.com/wirtschaft/49870-ostsee-pipeline-nord-stream-2-trotz-sanktionen-gebaut-russland-deutschland/]Search in Google Scholar
[6. http://rab.ict.pwr.wroc.pl/~arent/rr/mpr/czujniki2.html,]Search in Google Scholar
[7. http://www.tme.eu/pl/details/cw-18-10k-p6/potencjometry-jednoobrotowe-cermetowe/telpod/,]Search in Google Scholar
[8. Hupka J.: Pipeline operation related technical problems (in Polish), Department of Chemical Technology, Faculty of Chemistry, Gdansk University of Technology.]Search in Google Scholar
[9. Gerwatowski D.: Linear flow resistance coefficient vs. system flow capacity, with the Yamal pipeline as an example of transit pipeline system (in Polish), EuRoPol GAZ SA, Warsaw.]Search in Google Scholar
[10. Figures from Inventor programme.]Search in Google Scholar
[11. http://automatykab2b.pl/technika/3095-czujniki-tensometryczne-czyli-co-o-pomiarach-siy-powinien-wiedzie-automatyk#.VmstudLhC00,]Search in Google Scholar
[12. http://www.simex.pl/produkt/3313,]Search in Google Scholar
[13. Magda W.: Marine pipelines (in Polish), Wydawnictwo techniczne, Warsaw 2004.]Search in Google Scholar
[14. Nord Stream - Espoo Report, https://www.nord-stream.com]Search in Google Scholar
[15. http://www.nord-stream.com/]Search in Google Scholar
[16. https://www.youtube.com/watch?v=55wa_CvA7UA,]Search in Google Scholar
[17. http://www.bc.pollub.pl/Content/254/korozja.pdf]Search in Google Scholar
[18. http://www.tdwilliamson.com/SolutionsEngine?condition=99&industry=9,]Search in Google Scholar
[19. http://www.rosen-group.com/global/solutions/pipeline-systems.html,]Search in Google Scholar
[20. http://www.elesa-ganter.com/pl/28/sp/9563/4/120/kola-z-nalewanym-wie%C5%84cem-poliuretanowym/re.f5/eg/,]Search in Google Scholar