14351
The present study investigated the association of CHRNA5 polymorphisms and smoking topography in 66 smokers asked to smoke four nicotine - containing ( nicotine yield = 0 . 60 mg ) and four placebo ( nicotine yield < 0 . 05 mg ) cigarettes , during separate experimental sessions .
 Chemical: nicotine; Chemical: nicotine; Chemical: nicotine
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: nicotine; Chemical: nicotine; Chemical: nicotine