The following are a sample of some of the relevant reference books that focus more specifically on a time period or theological tradition or, in the case of the New Catholic Encyclopedia, encompass a very wide range of subjects, written from a specific theological tradition.
There are many others, some on similar periods (e.g., Early Christianity, Middle Ages, Modern), some on other traditions (e.g., Lutheranism, Catholicism, Pentecostalism, Methodism).
These works will help you identify some of the most important primary and secondary sources for your theologian, tradition, or doctrine.