“The Sabbath-School Index: Pointing out the history and progress of Sunday-schools, with approved modes of instruction” by R. G. Pardee is a notable reference for the history and development of Sunday-schools. Pardee's meticulous indexing provides insights into the growth and evolution of Sunday-schools, offering approved methods of instruction and emphasizing their significance. This book is a valuable source for those researching the history of religious education and the role of Sunday-schools in nurturing spiritual and moral development.