APA
American Gas Association A., . (1997). Fundamentals of Customer Service. Washington: American Gas Association, AGA.
Chicago
American Gas Association AGA, . 1997. Fundamentals of Customer Service. Washington: American Gas Association, AGA.
Harvard
American Gas Association A., . (1997). Fundamentals of Customer Service. Washington: American Gas Association, AGA.
MLA
American Gas Association AGA, . Fundamentals of Customer Service. Washington: American Gas Association, AGA. 1997.
