Harwood G. Kolsky: APLGOL - A Structured Programming Language for APL. pp161-191

Clemens Hackl (Ed.): Programming Methodology, 4th (1975) Clemens Hackl (Ed.): Programming Methodology, 4th Informatik Symposium, IBM Germany, Wildbad, September 25-27, 1974. Lecture Notes in Computer Science 23 Springer 1975  

Languages mentioned APLGOL {1972} APL with ALGOL-like control structures