Gaya APA
ENGELSOHN, H, S. (1981).
TRIGONOMETRY: A COMPLETE AND CONCRETE APPROACH .
United States of America.:
McGRAW-HILL.
Gaya MLA
ENGELSOHN, Harold, S..
"TRIGONOMETRY: A COMPLETE AND CONCRETE APPROACH".
United States of America.:
McGRAW-HILL,
1981.
Textbook.