Here is a link to one of the documents filed to the FEC on behalf of a liberal watchdog..https://freespeechforpeople.org/wp-content/uploads/2017/05/FSFP-FEC-Complaint-re-Russia-Trump-WEB.pdf

The FEC also has Mr. Trump on the hook for $19 million in undocumented campaign donations but he can't be criminally prosecuted for these.  He just has to pay them back.