Recursive data structures and related control mechanisms in APL. - W. E. Gull; Michael A. Jenkins (APL, 1976)

Decisions for "Type" in APL. - W. E. Gull; Michael A. Jenkins (POPL, 1979)

Recursive Data Structures in APL. - W. E. Gull; Michael A. Jenkins (Commun. ACM, 1979)