[1. Goodman, L. A.: On the exact variance of products; Journal of the American Statistical Association 55 (292), (1960) 708-713.10.1080/01621459.1960.10483369]Search in Google Scholar
[2. Weatherly, C. H., J. E. Kiefer: Instrument for simultaneous measurement of pressure drop and filter ventilation; Eastman Technical Information for Customer Dissemination, Filter Technology Report No. 64. ]Search in Google Scholar