"Birds as a Class". The Birds of Concord: A Study in Population Trends, Cambridge, MA and London, England: Harvard University Press, 1949, pp. 74-88. https://doi.org/10.4159/harvard.9780674284081.c6
(1949). Birds as a Class. In The Birds of Concord: A Study in Population Trends (pp. 74-88). Cambridge, MA and London, England: Harvard University Press. https://doi.org/10.4159/harvard.9780674284081.c6
1949. Birds as a Class. The Birds of Concord: A Study in Population Trends. Cambridge, MA and London, England: Harvard University Press, pp. 74-88. https://doi.org/10.4159/harvard.9780674284081.c6
"Birds as a Class" In The Birds of Concord: A Study in Population Trends, 74-88. Cambridge, MA and London, England: Harvard University Press, 1949. https://doi.org/10.4159/harvard.9780674284081.c6
Birds as a Class. In: The Birds of Concord: A Study in Population Trends. Cambridge, MA and London, England: Harvard University Press; 1949. p.74-88. https://doi.org/10.4159/harvard.9780674284081.c6