Nitrogen-fixing cyanobacteria (free-living and diatom endosymbionts): their use in southern California stream bioassessment - Rosalina Stancheva; Robert G. Sheath; Betsy A. Read; Kimberly D. McArthur; Chrystal Schroepfer; J. Patrick Kociolek; A. Elizabeth Fetscher (Hydrobiologia, 2013)