Fox's Book of Martyrs - John Foxe

Patrick and the Early Celtic Church - Brian Hoeck

The Sabbath Keepers of Transylvania - D Thomas Lancaster

Sabbatarians in Transylvania - Gerhard O. Marx 

A History of the True Church Traced from 33 A.D. to Date - Andrew N. Dugger and Clarence O. Dodd,  1972

History of the Seventh Day Church of God, Volume I - Richard C. Nickels, 1999  

History of the Seventh Day Church of God, Volume II - Compiled by Richard C. Nickels, 1973

Truth Triumphant: The Church in the Wilderness - Benjamin George Wilkinson, PH. D.

The Incredible History of God's True Church - Ivor Fletcher