27587
In Russia and the Soviet Union , the boundary along the Kuma–Manych Depression was the most commonly used as early as 1906 .
 Russia, Soviet Union, Kuma–Manych Depression
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Russia, Soviet Union, Kuma–Manych Depression