Campos, Patrick F
The University of the philippines Pres, 2016
Buku Teks
David, Joel
Anvil Pub, 1990
Buku Teks
Heider, Karl G.
University of Hawaii Press, 1991
Buku Teks
Crisp, L.F. (Leslie Finlay)
Longman Chesire, 1965
Buku Teks SO
Crisp, L.F. (Leslie Finlay)
Longman, 1973
Buku Teks SO