http://aurora.wells.edu/~wbac/bookarts/vhammer_about.html

http://aurora.wells.edu/~wbac/bookarts/wcpress.html

http://www.uky.edu/Libraries/KLP/tour.html

http://www.caxtonclub.org/reading/hammer.html

http://special.library.louisville.edu/display-collection.asp?ID=10

http://palimpsest.stanford.edu/byform/mailing-lists/exlibris/2002/02/msg00058.html

http://www.klingspor-museum.de/KlingsporKuenstler/Schriftdesigner/Hammer/VHammer.pdf

http://www.grolierclub.org/ExHammer.htm

http://www.klingspor-museum.de/Kuenstler.html