Sanders, E. P. Paul: A Very Short Introduction. Oxford University Press, June 7, 2001.
Writings of Apostle
Braunch, Manfred. Hard Sayings of Paul (Hard Sayings Series the Hard Sayings). IVP Academic, June 22, 1989.
Travel: Apostle travelled to various places such as Jerusalem, Damascus, Arabia, Syria, Caesarea. The references below help understand his travel.
Wellman, Jack. Apostle Peter Biography: Timeline, Life, and Death. November 12, 2011
Hengel, Martin. Paul between Damascus and Antioch: The Unknown Years. Westminster John Knox Press April 1, 1997
Collection of his letters: His Writings
J.D. Douglas, General Editor. The International Dictionary of the Christian Church. Zondervan Publishing House, 1978.
Polhill, John B. Paul and His Letters. B&H Academic , August 15, 1999.
Jesus, Paul, and Christianity: The connection and difference between Jesus and Paul. And the implication on how they approached Christianity
Wenham, David. Paul: Follower of Jesus or Founder of Christianity? Wm. B. Eerdmans Publishing Company; First Edition edition, April 1, 1995.
Wright, N.T. What Saint Paul Really Said: Was Paul of Tarsus the Real Founder of Christianity? Wm. B. Eerdmans Publishing Company; 1 edition, June 1997.
III, Ben Witherington. Jesus, Paul and the End of the World. IVP Academic, Print On Demand edition, April 13, 1992.
Smith, Dr. William. Smith's Bible Dictionary. 1884.
Murphy-O'Connor, Jerome. Paul: A Critical Life. Oxford University Press, September 3, 1998.
Bruce, F. F. Paul, apostle of the heart set free. Eerdmans, 2000.
III, Ben Witherington. The Paul Quest: The Renewed Search for the Jew of Tarsus. IVP Academic; First Edition, October 22, 2001.
Michael F. Bird (Editor), Stanley N. Gundry (Series Editor), Thomas R. Schreiner (Contributor). Four Views on the Apostle Paul (Counterpoints: Bible and Theology). Zondervan, July 28, 2012.