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Therefore the combination of aspirin and warfarin to improve prevention of atherothrombosis compared to antiplatelet therapy alone was studied but could not be established due to significantly increased risk of major bleeding compared to a nonsignificant reduction in ischemic events .
 Chemical: aspirin; Chemical: warfarin
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: aspirin; Chemical: warfarin