1. L. Auslander, On a problem of Philip Hall. Ann. Math. (2) 86, 112–116 (1967). MR0218454
2. G. Baumslag, Lecture Notes on Nilpotent Groups. Regional Conference Series in Mathematics, No. 2 (American Mathematical Society, Providence, RI, 1971). MR0283082
3. E. Formanek, A short proof of a theorem of Jennings. Proc. Am. Math. Soc. 26, 405–407 (1970). MR0272895
4. P. Hall, The Edmonton Notes on Nilpotent Groups. Queen Mary College Mathematics Notes. Mathematics Department (Queen Mary College, London, 1969). MR0283083
5. B. Hartley, The residual nilpotence of wreath products. Proc. Lond. Math. Soc. (3) 20, 365–392 (1970). MR0258966