Van Doren, Carl. Benjamin Franklin, The Viking Press, New York, 1938. p. 159. Quoted text from May 1751 letter published in "Gentleman's Magazine" at http://www.matLưu trữ 2013-07-13 tại Wayback Machineh.tamu.edu/~stecher/489/Ben/science.shtml.[1]Lưu trữ 2016-03-04 tại Wayback Machine
Van Doren, Carl. Benjamin Franklin, The Viking Press, New York, 1938. p. 159. Quoted text from May 1751 letter published in "Gentleman's Magazine" at http://www.matLưu trữ 2013-07-13 tại Wayback Machineh.tamu.edu/~stecher/489/Ben/science.shtml.[1]Lưu trữ 2016-03-04 tại Wayback Machine
web.archive.org
Van Doren, Carl. Benjamin Franklin, The Viking Press, New York, 1938. p. 159. Quoted text from May 1751 letter published in "Gentleman's Magazine" at http://www.matLưu trữ 2013-07-13 tại Wayback Machineh.tamu.edu/~stecher/489/Ben/science.shtml.[1]Lưu trữ 2016-03-04 tại Wayback Machine