The Grove Encyclopedia of Medieval Art and Architecture, Volume 1. / Edit. Colum Hourihane. — OUP USA, 2012. P. 221.
Mori J. Crosses of Many Cultures. — Harrisburg, 1998. P. 38.
Benker S. Liturgische Geräte, Kreuze und Reliquiare der christlichen Kirchen / Objets liturgiques, croix et reliquaires des eglises chretiennes. Walter de Gruyter, 2011. S. 68.
Королев К. Энциклопедия символов, знаков, эмблем. — Мидгард, 2005. С. 314.
Liungman C. G. Symbols — Encyclopedia of Western Signs and Ideograms. Ionfox AB. — HME Publishing, 2004. P. 140. ISBN 978-91-972705-0-2.