Mastery Exercise: Find concise summary of genes pertaining to a specific area of research

I have received a Request for Proposals on the topic of circadian rhythms. I'd like to study the regulation of a gene important in circadian rhythms, but I haven't decided which gene to follow. I went to Entrez Nucleotide, entered "circadian" and found 668 references--too many! Also, many entries are redundant. How can I get a concise summary of potential genes to follow?