Based on context I would assume it is:

A Call by Need Lambda Calculus.

Zena Ariola, Matthias Felleisen, John Maraist, Martin Odersky, and Philip Wadler. 22'nd Symposium on Principles of Programming Languages, ACM Press, San Francisco, California, January 1995.

There is a humorous story about how the paper and collaboration came about, which Felleisen discusses in an interview [1].

[1] —> https://www.cs.cmu.edu/~popl-interviews/felleisen.html