Finding Websites From Company Name

I've got a list of 6,000 company names (along with their headquarters address) 开发者_Go百科and I need to find the web address for each of them. I'm considering using the Google Web API (obviously this will take a few days as only 1,000 queries per day are allowed) to do this(search for "COMPANY_NAME CITY STATE") and then take the first result. However I'm not 100% sure this will work, and I feel like there's a better way. I can do this in any language I know really, C++, Java, PHP, Python. This only has to be run once.

How would I use WHOIS to do this? I know how I would do it if I already knew the URL, but not the other way around(name to URL). And what would I do if it were privately registered?

BTW, these are US businesses.

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You can use WHOIS instead of Google API for it.

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Use Amazons Mechanical Turk. It's perfect for these kinds of tasks which can be hard to automate and typically need a person to validate them. It will cost a little but it should be manageable, depending on how bad you want the results.