Perhaps you should try some spelling variations:
formulation problems » formulation problem, formation problems, population problems
integer formulation » integral formulation, integral formulations, integer permutations
microarray https » microarrays https, microarray chips, microscopy https
code microarray » wide microarray, course microarray, color microarray
problems code » problems node, problems model, problems case

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• Performing a fuzzy search may retrieve terms with similar spellings: integer formulation problems code microarray https~.
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