Sources:

Henry Chadwick - The Early Church

Justo Gonzalez - A History of Christian Thought

Frances M. Young - From Nicaea to Chalcedon

John Behr - The Nicene Faith

normalhistory.com

Sources:

Henry Chadwick: The Early Church

Justo Gonzales: Early Christian Thought

Michael Haykin: Defending the Truth

Michael Kruger: Christianity at the Crossroads

Sources:

The Early Church by Henry Chadwick

Christianity at the Crossroads by Michael Kruger

Rediscovering the Church Fathers by Michael Haykin

A History of Christian Thought by Justo Gonzalez

Sources:

Justo Gonzalez A History of Christian Thought

Michael Haykin Rediscovering the Church Fathers

Frederick Weidmann Polycarp and John

Henry Chadwick The Early Church

Jaroslav Pelikan The Emergence of the Catholic Tradition (100-600)