16422
In order to determine an accurate equilibrium structure for 1 , 3 , 4 - oxadiazole , microwave transitions and ground - state rotational constants are reported for the parent species and for the ( 18 ) O isotopologue measured in natural abundance .
 Chemical: 1 , 3 , 4 - oxadiazole; Chemical: ( 18 ) O
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: 1 , 3 , 4 - oxadiazole; Chemical: ( 18 ) O