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Discovery of aryl ureas and aryl amides as potent and selective histamine H3 receptor antagonists for the treatment of obesity ( Part I ) .
 Chemical: aryl ureas; Chemical: aryl amides; Chemical: histamine
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: aryl ureas; Chemical: aryl amides; Chemical: histamine