18705
We have induced liver tumors in mice by treatment with the liver carcinogen N - nitrosodiethylamine followed by chronic treatment with the tumor promoter phenobarbital .
 Chemical: N - nitrosodiethylamine; Chemical: phenobarbital
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: N - nitrosodiethylamine; Chemical: phenobarbital