Copyright searches are done by specialty firms, publishers and attorneys in copyright issues but, a little known secret is that you can go directly to the Copyright Office and request a copyright search and even have it certified by the CO staff.
You can also search online now, but the results are NOT as accurate as having the Copyright office perform this for you. The online search should not be used as a definitive answer to your copyright question, but only as a guide.
My suggestion is to use the online search as a general guide and then, if it appears your work (if its found) is in the public domain to get the Copyright Office to conduct a search as well. The important thing to remember is that if youre going to use the work in a commercial venture to make sure you get a written certified copyright report from the US Copyright Office.
Author Resell Rights Publisher Publication Date 2010-07-15 Binding Kindle Edition ISBN Number Of Pages Sales Rank 117321