50966
His name was restored only in the mid-1980 's , when Mikhail Gorbachev , citing Khrushchev as a mentor , began the liberal changes that ultimately brought about the collapse of the Soviet Union in 1991 .
 Mikhail Gorbachev, Soviet Union
Please list all entity pairs containing a certain relationship in the given options.Output format is "word1, word2; word3, word4". 
Option: ethnicity, place lived, geographic distribution, company industry, country of administrative divisions, administrative division of country, location contains, person of company, profession, ethnicity of people, company shareholder among major shareholders, sports team of location, religion, neighborhood of, company major shareholders, place of death, nationality, children, company founders, company founded place, country of capital, company advisors, sports team location of teams, place of birth 
Text: {0} 
Answer:
 Mikhail Gorbachev, Soviet Union