Crocker, Lester G. (1957). "Review of The Age of Ideas by George R. Havens". The Journal of Modern History. 29 (2): 125–126. doi:10.1086/238001. ISSN0022-2801.
Crocker, Lester G. (1957). "Review of The Age of Ideas by George R. Havens". The Journal of Modern History. 29 (2): 125–126. doi:10.1086/238001. ISSN0022-2801.