Foster, R. J. (1999). Physical Geology (20th ed.). Charles E. Merrill.
Chicago-čujuhus (17. p.)Foster, Robert J. Physical Geology. 20th ed. Columbus: Charles E. Merrill, 1999.
MLA-čujuhus (9. p.)Foster, Robert J. Physical Geology. 20th ed. Charles E. Merrill, 1999.
Muitte dárkkistit čujuhemiid riektatvuođa, ovdal go geavahat daid iežat deavsttas.