On the Structure of Nonstandard Models of Arithmetic, Proceedings of
the American Mathematics Society, Vol. 27 no. 2 1971.
Elementary Extensions of Linear Topological Abelian Groups (with P.L.
Sperry), Proceedings of the American Mathematical Society, Vol. 31 no.
2, 1972 .
Addition in Non-Standard Models of Arithmetic, Journal of Symbolic
Logic, Vol. 37, no. 3, 1972.
Omitting Types in Arithmetic and Conservative Extensions, published as
part of the Symposium on Non-standard Analysis held at the University
of Victoria, Victoria, B.C., Canada, May 8-11, 1972, by the
Springer-Verlag Lecture Note Series ,Vol. 369, 1974
A Minimal Extension that is not Conservative, Michigan Mathematical
Journal, Vol. 21, 1974
