- earlychurchhistory.org martyrs/
- famouswonders.com church-of-the-holy-apostles/
- archive.org details/holy-martyrs-of-gorcum-church
- getslimsecret.com radiant/wiki/Bydgoszcz_CathedralSt. Martin and St. Nicholas Cathedral (Polish: Katedra św. Marcina i Mikołaja), or simply known as Bydgoszcz Cathedral, is a Catholic church built in the 15th century.
- http://romeofthewest.com 2005/12/photos-of-church-of-…
- sacred-destinations.com turkey/istanbul-church-of…
- madainproject.com church_of_the_holy_sepulchre
- nelmitravel.com the-holy-cross-church-in-warsaw-…