Today the 31st of January 2019 there was a vote in the European Parliament on the topic of transparency with regards to contacts with lobbyists (link in swedish). This vote was decided to be cast anonymously, which can be done if more than one fifth of the MEP's want to.
Who voted for having an anonymous vote? Official sources are a great plus.
I cannot find the vote at the European Parliament web page.
VoteWatch.eu as suggested in another answer gives a 502 error, so this is not an option.