First and foremost, I thank my wife and colleague, Corinne Manogue, for discussions and encouragement over many years. Her struggles with the traditional language of differential geometry, combined with her insight into how undergraduate physics majors learn — or don't learn — vector calculus have been a major influence on my increased use of differential forms and orthonormal bases in the classroom.

I thank my department for encouraging the development of an undergraduate mathematics course in general relativity, then supporting this course over many years. I am also grateful for the support and interest of numerous students, and for their patience as I experimented with several textbooks, including my own.