16744
ESEM - EDX analysis determined the calculus to be predominantly composed of calcium hydroxyapatite and cholesterol , as indicated by the petrous surface and drop - like nodules / crystals , respectively .
 calcium hydroxyapatite, cholesterol
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 calcium hydroxyapatite, cholesterol