The primary factors of organic evolution - Cope, E. D. (Edward Drinker), 1840 -1897 (The Open Court Publishing Company, 1896)

Primitive animals - Smith, Geoffrey, 1881 -1916 (The University press, 1911)

Principles of animal biology - Shull, A. Franklin (Aaron Franklin), 1881 -1961 (McGraw-Hill, 1920)

Principles of animal biology - Shull, A. Franklin (Aaron Franklin), 1881 -1961 (McGraw-Hill book company, inc, 1946)

The principles of biology - Spencer, Herbert, 1820 -1903 (D. Appleton, 1899)

The principles of biology - Spencer, Herbert, 1820 -1903 (D. Appleton, 1896)

The principles of biology - Spencer, Herbert, 1820 -1903 (D. Appleton, 1910)

The principles of biology - Spencer, Herbert, 1820 -1903 (D. Appleton and company, 1898)

Principles of economic zoölogy - Daugherty, L. S. (Lewis Sylvester) 1857 -1919 (W. B. Saunders Company, 1917)

Principles of economic zoo̤logy - Daugherty, L. S. (Lewis Sylvester) 1857 -1919 (W.B. Saunders, 1915)