International Association of Paper Historians (2013), International standard for the registration of papers with or without watermarks: version 2.1, Marburg, IPH. http://www.paperhistory.org/Standards/IPHN2.1.1_en.pdf (accessed June 2015)
International Association of Paper Historians (2013), International standard for the registration of papers with or without watermarks: version 2.1, Marburg, IPH. http://www.paperhistory.org/Standards/IPHN2.1.1_en.pdf (accessed June 2015)