11997
The cause of the crash of the helicopter , which went down on Sunday while on a routine resupply flight between Phnom Penh and Stung Treng , was not known .
 Stung Treng, Phnom Penh
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, else, organization, person 
Text: {0} 
Answer:
 Stung Treng, Phnom Penh