21890
By 1973 , after their second child was born , it had become clear to Ms. Volokh and her husband Vladimir , a computer scientist , that they wanted to leave the U.S.S.R .
 1973, second, Volokh, Vladimir, U.S.S.R
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: date, organization, person, geographical social political, national religious political, facility, cardinal, location, work of art, law, event, product, ordinal, percent, time, quantity, money, language 
Text: {0} 
Answer:
 1973, second, Volokh, Vladimir, U.S.S.R