Question:
Which employer did Rudy Wijnands work for in Apr, 1999?

Context:
 Rudy Wijnands works for Massachusetts Institute of Technology from Sep, 1999 to Aug, 2002. 
 Rudy Wijnands works for University of Amsterdam from Feb, 1999 to Aug, 1999. 
 Rudy Wijnands works for University of St Andrews from Sep, 2002 to Sep, 2003.

Answer:
University of Amsterdam