Properties preserved under recursion removal. - H. Raymond Strong; S. A. Walker (Proving Assertions About Programs, 1972)

Characterization of Flowchartable Recursions (Short Version) - S. A. Walker; H. Raymond Strong (STOC, 1972)

Characterizations of Flowchartable Recursions. - S. A. Walker; H. Raymond Strong (J. Comput. Syst. Sci., 1973)