Question:
Who was the head of Cologne in Dec, 1968?

Context:
 John van Nes Ziegler is the head of the government of Cologne from Dec, 1973 to Oct, 1980. 
 Henriette Reker is the head of the government of Cologne from Oct, 2015 to Dec, 2022. 
 Jürgen Roters is the head of the government of Cologne from Oct, 2009 to Oct, 2015. 
 Fritz Schramma is the head of the government of Cologne from Sep, 2000 to Oct, 2009. 
 Norbert Burger is the head of the government of Cologne from Oct, 1980 to Sep, 1999. 
 Ernst Schwering is the head of the government of Cologne from Nov, 1951 to Nov, 1956. 
 Robert Görlinger is the head of the government of Cologne from Nov, 1950 to Nov, 1951. 
 Theo Burauen is the head of the government of Cologne from Nov, 1956 to Dec, 1973.

Answer:
Question:
Who was the head of Cologne in Dec, 1968?

Context:
 John van Nes Ziegler is the head of the government of Cologne from Dec, 1973 to Oct, 1980. 
 Henriette Reker is the head of the government of Cologne from Oct, 2015 to Dec, 2022. 
 Jürgen Roters is the head of the government of Cologne from Oct, 2009 to Oct, 2015. 
 Fritz Schramma is the head of the government of Cologne from Sep, 2000 to Oct, 2009. 
 Norbert Burger is the head of the government of Cologne from Oct, 1980 to Sep, 1999. 
 Ernst Schwering is the head of the government of Cologne from Nov, 1951 to Nov, 1956. 
 Robert Görlinger is the head of the government of Cologne from Nov, 1950 to Nov, 1951. 
 Theo Burauen is the head of the government of Cologne from Nov, 1956 to Dec, 1973.

Answer:
user
Theo Burauen
assistant
Question:
Who was the head of Cologne in Dec, 1968?

Context:
 John van Nes Ziegler is the head of the government of Cologne from Dec, 1973 to Oct, 1980. 
 Henriette Reker is the head of the government of Cologne from Oct, 2015 to Dec, 2022. 
 Jürgen Roters is the head of the government of Cologne from Oct, 2009 to Oct, 2015. 
 Fritz Schramma is the head of the government of Cologne from Sep, 2000 to Oct, 2009. 
 Norbert Burger is the head of the government of Cologne from Oct, 1980 to Sep, 1999. 
 Ernst Schwering is the head of the government of Cologne from Nov, 1951 to Nov, 1956. 
 Robert Görlinger is the head of the government of Cologne from Nov, 1950 to Nov, 1951. 
 Theo Burauen is the head of the government of Cologne from Nov, 1956 to Dec, 1973.

Answer:
user
Ernst Schwering
John van Nes Ziegler
Fritz Schramma
Jürgen Roters
Norbert Burger
Henriette Reker
Robert Görlinger
assistant
Question:
Who was the head of Cologne in Dec, 1968?

Context:
 John van Nes Ziegler is the head of the government of Cologne from Dec, 1973 to Oct, 1980. 
 Henriette Reker is the head of the government of Cologne from Oct, 2015 to Dec, 2022. 
 Jürgen Roters is the head of the government of Cologne from Oct, 2009 to Oct, 2015. 
 Fritz Schramma is the head of the government of Cologne from Sep, 2000 to Oct, 2009. 
 Norbert Burger is the head of the government of Cologne from Oct, 1980 to Sep, 1999. 
 Ernst Schwering is the head of the government of Cologne from Nov, 1951 to Nov, 1956. 
 Robert Görlinger is the head of the government of Cologne from Nov, 1950 to Nov, 1951. 
 Theo Burauen is the head of the government of Cologne from Nov, 1956 to Dec, 1973.

Answer:
user
Theo Burauen
assistant