27787
Finally , we made preliminary two - dimensional ( 2D ) calculations of the cross sections for rotationally inelastic H - CO collisions with the CO bond length fixed and obtained good agreement with recently published 2D results .
 H, CO, CO
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 H, CO, CO