W. & F. Langenheim n.d. The Lord's Prayer - Containing 268 letters in a space the one thousand part of a square inch. and almost invisible by the naked eye. Made by W. F. Langenheim, Philadelphia
Photomicrograph, slide Private collection of Herbert C. McKay Photographs prepared by Herbert C. McKay and kindly provided by his grandson Maurice M. Greeson (19 June 2012).
