Question:
Which employer did J. M. Wallace-Hadrill work for in Jun, 1957?

Context:
 J. M. Wallace-Hadrill works for Merton College from Jan, 1961 to Jan, 1974. 
 J. M. Wallace-Hadrill works for University of Manchester from Jan, 1955 to Jan, 1961. 
 J. M. Wallace-Hadrill works for University of Oxford from Jan, 1974 to Jan, 1983. 
 J. M. Wallace-Hadrill works for All Souls College from Jan, 1974 to Jan, 1985.

Answer:
University of Manchester