22891
This study also reveals , for the first time , the ability to distinguish between P - O and P [ double bond , length as m - dash ] O bonding in these rare - earth phosphate glasses from X - ray diffraction data in a fully quantitative manner .
 P - O, P, O, rare - earth phosphate
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 P - O, P, O, rare - earth phosphate