Question:
Which employer did Sonja Brentjes work for in Jun, 2001?

Context:
 Sonja Brentjes works for University of Oklahoma from Jan, 2002 to Jan, 2003. 
 Sonja Brentjes works for Goethe University Frankfurt from Jan, 1999 to Jan, 2002. 
 Sonja Brentjes works for Leipzig University from Jan, 1976 to Jan, 1997. 
 Sonja Brentjes works for Ludwig Maximilian University of Munich from Jan, 2007 to Jan, 2007.

Answer:
Goethe University Frankfurt