An assessment of stressor extent and biological condition in the North American mid-continent great rivers (USA) - Angradi, Ted; Bolgriend, David; Jicha, Terri; Pearson, Mark; Taylor, Debra; Moffett, Mary; Blocksom, Karen; Walters, David M.; Elonen, Colleen; Anderson, Leroy; Lazorchak, James; Reavie, Euan; et al. (River Systems, 2011)