The Truth About ‘Spying’ on the Trump Campaign
https://www.nytimes.com/2019/05/03/opinion/trump-campaign-spying-fbi-russia-.html
The F.B.I. used an undercover investigator — the research assistant, who went by the name Azra Turk — and Stefan Halper, a professor in Britain and longtime informant, to make contact with Mr. Papadopoulos (Mr. Halper also made contact with two other campaign officials, Sam Clovis and Carter Page).