Brown, Wayne C., and Barry J. Shepherd. Graphics File Formats Reference and Guide. Greenwich, CT: Manning Publications, 1992.
Kay, David C. and John R. Levine. Graphics File Formats. Windcrest Books, 1992.
Kay, David C. and John R. Levine. Graphics File Formats. 2d ed. Windcrest/McGraw-Hill, 1995.
Murray, James D., and William vanRyper. Encyclopedia of Graphics File Formats. Sebastapol, CA: O'Reilly & Associates, Inc., 1994.
Murray, James D. and William vanRyper. Encyclopedia of Graphics File Formats, 2d ed. Sebastopol, CA: O'Reilly & Associates, Inc., 1996.
Petzold, Charles. Programming Windows: The Microsoft Guide to Writing Applications for Windows 3. Redmond, WA: Microsoft Press, 1990.
Wegner, Tim. "Coding for PNG Graphics", PC Techniques (Feb/Mar 1996): 32-38.
"Graphic Image Format FAQ 3-4." James D. Murray, 1994-1996.
PBM, PGM, PPM, PNM Specifications by Jef Poskanzer, copyright " 1989, 1991.
PNG (Portable Network Graphics), tenth draft. Page 5, copyright Thomas Boutell, May 1995.