Eaton, Anne Thaxter. "Widening Horizons, 1840-1890." In A Critical History of Children's Literature, edited by Cornelia Meigs. New York: Macmillan, 1953. This book includes a good brief discussion of the appeal of Heidi.

Eayrs, Catherine. "Johanna Spyri." In Writers for Children: Critical Studies of Major Authors Since the Seventeenth Century, edited by Jane M. Bingham.

New York: Charles Scribner's Sons, 1988. This article provides a good biography of Spyri, along with an analysis of her style, autobiographical elements in her writing, cultural and historical background, and reception by critics.

"Heidi—or the Story of a Juvenile Best Seller." Publisher's Weekly (July 5, 1953): 318-321. This article, written on the occasion of Heidi's 75th birthday, explores the book's publication history and the reasons for its continued popular success. It also provides some interesting biographical details, especially concerning Spyri's childhood.

Kunitz, Stanley J., and Howard Haycraft, eds. The Junior...