Gaya APA
Picard, W, L, S, S, J, M, D. (1978).
Introcution to Geology, Physical and Historical .
London:
Prentice-Hall, Inc.
Gaya MLA
Picard, William, Lee, Stokes, Sheldon, Judson, M, Dane.
"Introcution to Geology, Physical and Historical".
London:
Prentice-Hall, Inc,
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.