Looking for Olde Books Revealing the History of Mathematics
An increasing number of on-line data bases are becoming available. The MathNEXUS website is an example of such. In fact, on-line data bases are a natural idea that should become more and more evident...and used.
Specific to the history of mathematics, you might be interested in finding an original "primary" document (assuming you can read multiple languages)...or perhaps a related translation or article. To your rescue, consider these valuable on-line data bases:
Admittedly, these are not web resources that you will use on a regular basis...but, this listing is provided just in case you ever need to sue it. Plus, it serves as my personal list that is accessible when needed.