14540
Because of difficulties in recruiting sufficient mitochondrial disease patients and the relatively large expense of conducting such trials , advantageous strategies include crossover designs ( where possible ) , multicenter collaboration , and the selection of very few , clinically relevant , primary outcomes .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
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