TY  - RPRT
TI  - Observer differences in the North American Breeding Bird Survey
AU  - J.R. Sauer
AU  - B.G. Peterjohn
AU  - W.A. Link
PY  - 1994
DO  - 10.2307/4088504
UR  - https://pubs.usgs.gov/publication/5222733
ID  - 5222733
ER  -