P. A. Loeb, Conversion from nonstandard to standard measure and applications in probability theory, 1975

A. E. Hurd, P. A. Loeb, Introduction to nonstandard real analysis, Acad. Press 1985.

Sergio Albeverio, Jens Erik Fenstad, Raphael Hoegh-Krohn, Nonstandard methods in stochastic analysis and mathematical physics, Academic Press 1986 (there is also a Dover 2009 edition and a 1990 Russian translation)