APA (7th ed.) Citation
Varis, L. (2011). Mastering exposure and the zone system for digital photographers. Course Technology PTR.
Chicago Style (17th ed.) Citation
Varis, Lee. Mastering Exposure and the Zone System for Digital Photographers. Boston, Mass., U.S.A.: Course Technology PTR, 2011.
MLA (9th ed.) Citation
Varis, Lee. Mastering Exposure and the Zone System for Digital Photographers. Course Technology PTR, 2011.
Warning: These citations may not always be 100% accurate.