Is there a "scientific" online source for famous direct qoutes? I'm searching for an online source that is considered "scientific" to look up some well-known quotes such as "There's no such thing as a free lunch." (Milton Friedman).

I may want to use kind of an insinuating quote about risk in my term paper.
How about Quotedb? It seems awfully relevant although risk might be quite a specialized area to be included in it. Quotes tend to be rather general.