The Lemon Fool

Can anyone point me to a freely available data source for evaluating performance of PE funds over the longer term?

Daughter's boyfriend is thinking of making this the topic of his dissertation, but is struggling with data sources

https://en.m.wikipedia.org/wiki/Private_equity

Maybe something to be gleaned here ...and see the 108 refs at the bottom of the article.

Maybe these refs will make ref to other sources?