APA

(19). I. C. S. reference library : a series of textbooks prepared for the students of the international correspondence schools and containing in permanent form the instruction papers, examination questions, and keys used in their various courses. s.l: Scranton International Textbook Company.

Chicago

19. I. C. S. reference library : a series of textbooks prepared for the students of the international correspondence schools and containing in permanent form the instruction papers, examination questions, and keys used in their various courses. s.l: Scranton International Textbook Company.

Harvard

(19). I. C. S. reference library : a series of textbooks prepared for the students of the international correspondence schools and containing in permanent form the instruction papers, examination questions, and keys used in their various courses. s.l: Scranton International Textbook Company.

MLA

I. C. S. reference library : a series of textbooks prepared for the students of the international correspondence schools and containing in permanent form the instruction papers, examination questions, and keys used in their various courses. s.l: Scranton International Textbook Company. 19.