Jonas Långmark; Nicholas J Ashbolt; Ulrich Szewzyk; Thor Axel Stenström (2001). "Adequacy of in situ glass slides and direct sand extractions to assess the microbiota within sand columns used for drinking water treatment". Canadian Journal of Microbiology. 47 (7): 601–607. doi:10.1139/w01-052. PMID11547879.
Jonas Långmark; Nicholas J Ashbolt; Ulrich Szewzyk; Thor Axel Stenström (2001). "Adequacy of in situ glass slides and direct sand extractions to assess the microbiota within sand columns used for drinking water treatment". Canadian Journal of Microbiology. 47 (7): 601–607. doi:10.1139/w01-052. PMID11547879.