المؤلفون: Engels, William L., McIntyre, Raymond W., Gunter, Gordon, Ulmer,, Frederick A., Halloran, Arthur F., Trapido, Harold, Kezer, James, Green, Morton, Foote, Leonard E., Lewis, John B., Rysgaard, G. N., Terres, J. Kenneth, Hubbard, Douglass H., Gerberg, Eugene J., Goble, Frans C., Allen, Durward L., Cook, Arthur H.

المصدر: Journal of Mammalogy, 1941 Nov 01. 22(4), 447-456.

الوصول الحر: https://www.jstor.org/stable/1374941Test

المؤلفون: Hudson, George E., Huey, Laurence M., Mohr, Charles E., Poole, Earl L., Ashcraft, Granville P., Wight, H. M., Engels, William L., Bailey, Florence Merriam, Howell, Arthur H., Orr, Robert T., Saunders, Aretas A., Seton, Ernest Thompson, Gordon, Kenneth, Shepherd, George S.

المصدر: Journal of Mammalogy, 1932 May 01. 13(2), 159-172.

الوصول الحر: https://www.jstor.org/stable/1374054Test

المؤلفون: Engels, William L.

المصدر: The American Midland Naturalist, 1936 May 01. 17(3), 653-660.

الوصول الحر: https://www.jstor.org/stable/2419940Test

المؤلفون: Engels, William L.

المصدر: The American Midland Naturalist, 1933 Jan 01. 14(1), 1-16.

الوصول الحر: https://www.jstor.org/stable/2420047Test