Publisher: MIT OpenCourseWare (official distribution).
Online text: ocw.mit.edu/courses/6-042j-mathematics-for-computer-science-spring-2015/mit6_042js15_textbook.pdf
The inspected online textbook is dated 18 May 2015; this is a version date, rather than a claim about first publication.
Cited passages: Lehman, Leighton and Meyer, Mathematics for Computer Science, Definition 11.7.1; Lehman, Leighton and Meyer, Mathematics for Computer Science, §11.8.1: cycles and backtracking; Lehman, Leighton and Meyer, Mathematics for Computer Science, §11.8.1: length-zero convention; Lehman, Leighton and Meyer, Mathematics for Computer Science, §§9.2 and 11.8.1: closed walks; Mathematics for Computer Science, §12.4, Lemma 12.4.1, printed p. 485; Mathematics for Computer Science, §12.4, Lemma 12.4.2 and Theorem 12.4.3, printed pp. 485–486; Mathematics for Computer Science, §12.5, Lemma 12.5.2 and Theorem 12.5.3, printed pp. 486–487.