Latin is not the source of 90% of European languages. Latin is the source of the Romance languages, which do not include the Germanic languages (of which English is one) nor the Slavic languages. Latin has influenced the Germanic and Slavic languages, the former far more than the latter, but it is absurd to say that Latin is the source of 90# of European languages.
The American Heritage Dictionary always had an extensive section on Indo-European roots, and clicking on this link
will take you to an online copy of the AH Dictionary's Indo-European roots appendix.
The company which publishes it also publishes The American Heritage Dictionary of Indo-European Roots
. (This link to an Amazon page is provided for information only, and does not constitute a recommendation of Amazon's products or services.)