Question:
Who was the head of Dortmund in Jun, 1992?

Context:
 Günter Samtlebe is the head of the government of Dortmund from Feb, 1973 to Sep, 1999. 
 Ullrich Sierau is the head of the government of Dortmund from May, 2010 to Oct, 2020. 
 Thomas Westphal is the head of the government of Dortmund from Nov, 2020 to Dec, 2022. 
 Gerhard Langemeyer is the head of the government of Dortmund from Oct, 1999 to Oct, 2009.

Answer:
Günter Samtlebe