Question:
Who was the head of Sofia in Jul, 1949?

Context:
 Boyko Borisov is the head of the government of Sofia from Nov, 2005 to Jul, 2009. 
 Stefan Sofiyanski is the head of the government of Sofia from Nov, 1995 to Jun, 2005. 
 Todor Zhivkov is the head of the government of Sofia from May, 1949 to Nov, 1949. 
 Aleksandar Karakachanov is the head of the government of Sofia from Oct, 1990 to Oct, 1991.

Answer:
Question:
Who was the head of Sofia in Jul, 1949?

Context:
 Boyko Borisov is the head of the government of Sofia from Nov, 2005 to Jul, 2009. 
 Stefan Sofiyanski is the head of the government of Sofia from Nov, 1995 to Jun, 2005. 
 Todor Zhivkov is the head of the government of Sofia from May, 1949 to Nov, 1949. 
 Aleksandar Karakachanov is the head of the government of Sofia from Oct, 1990 to Oct, 1991.

Answer:
user
Todor Zhivkov
assistant
Question:
Who was the head of Sofia in Jul, 1949?

Context:
 Boyko Borisov is the head of the government of Sofia from Nov, 2005 to Jul, 2009. 
 Stefan Sofiyanski is the head of the government of Sofia from Nov, 1995 to Jun, 2005. 
 Todor Zhivkov is the head of the government of Sofia from May, 1949 to Nov, 1949. 
 Aleksandar Karakachanov is the head of the government of Sofia from Oct, 1990 to Oct, 1991.

Answer:
user
Aleksandar Karakachanov
Stefan Sofiyanski
Boyko Borisov
assistant
Question:
Who was the head of Sofia in Jul, 1949?

Context:
 Boyko Borisov is the head of the government of Sofia from Nov, 2005 to Jul, 2009. 
 Stefan Sofiyanski is the head of the government of Sofia from Nov, 1995 to Jun, 2005. 
 Todor Zhivkov is the head of the government of Sofia from May, 1949 to Nov, 1949. 
 Aleksandar Karakachanov is the head of the government of Sofia from Oct, 1990 to Oct, 1991.

Answer:
user
Todor Zhivkov
assistant