Gaya APA
Heyworth, D, R, M. (2007).
Science In Focus Chemistry 'O' Level 2 nd edition thoey Workbook .
Singapore:
Pearson Longman.
Gaya MLA
Heyworth, Dr, Rex, M.
"Science In Focus Chemistry 'O' Level 2 nd edition thoey Workbook".
Singapore:
Pearson Longman,
2007.
Text.