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The aim of this work was to decipher the chemical structure of non - polar dimers formed during beta - sitosterol oxidation at 180 degrees C in the presence of oxygen .
 Chemical: beta - sitosterol; Chemical: oxygen
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: beta - sitosterol; Chemical: oxygen