Publisher: MIT OpenCourseWare (official distribution).
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.
Publisher: MIT OpenCourseWare.
Lecture 5f of MIT 6.042J and 18.062J, Mathematics for Computer Science, dated 7 October 2005. Authorship is credited to this slide deck, rather than to every resource in the course.
Cited passages: Planar Graphs; Bipartite Matching, slide lec 5f.6, including the outer face; Planar Graphs; Bipartite Matching, slides lec 5f.14–5f.15; Planar Graphs; Bipartite Matching, slides lec 5f.3 and 5f.12.