1. The Design of APL
2. The evolution of APL
3. The American Heritage Dictionary of the English Language Houghton Mifflin Company. The American Heritage Dictionary of the English Language Houghton Mifflin Company.
4. Berry P. C. SHARP APL Pocket Reference Toronto I.P. Sharp Associates 1984. Publication 0199 8409 E3 R1. Berry P. C. SHARP APL Pocket Reference Toronto I.P. Sharp Associates 1984. Publication 0199 8409 E3 R1.