Martin Luther (10 November 1483 – 18 February 1546) was a German monk, priest, professor of theology and iconic figure of the Protestant Reformation. He strongly disputed the claim that freedom from God's punishment for sin could be purchased with money. He confronted indulgence salesman Johann Tetzel with his Ninety-Five Theses in 1517. His theology challenged the authority and office of the Pope by teaching that the Bible is the only source of divinely revealed knowledge from God.
The Five Solas identified the distinctive theological positions held by the reformers and continue to serve as distinguishing characteristics of Reformed Theology. Here is a brief description of each, as well as links to additional information. http://reasonabletheology.org/five-solas
John Calvin (1509–1564) was an influential French theologian and pastor during the Protestant Reformation. He was a principal figure in the development of the system of Christian theology later called Calvinism. John Calvin was Martin Luther's successor as the preeminent Protestant theologian. Calvin made a powerful impact on the fundamental doctrines of Protestantism, and is widely credited as the most important figure in the second generation of the Protestant Reformation.
Dr. SINCLAIR FERGUSON (born 1948) is a Scottish theologian known in Reformed Christian circles for his teaching, writing, and editorial work. He is one of the most-respected Reformed theologians in the world today. He earned his M.A., B.D., and Ph.D. from the University of Aberdeen. He taught systematic theology full-time at Westminster Theological Seminary in Philadelphia for many years and continues to teach there as a visiting professor, and teaching fellow for Ligonier Ministries.