Harker, A. (1902). Petrology for students: An introduction to the study of rocks under the microscope (3rd ed.). University Press.

Harker, Alfred. Petrology for Students: An Introduction to the Study of Rocks Under the Microscope. 3rd ed. Cambridge: University Press, 1902.

Harker, Alfred. Petrology for Students: An Introduction to the Study of Rocks Under the Microscope. 3rd ed. University Press, 1902.