Journals of the Mutual UFO Network, the largest UFO organisation in the USA, are available online.
A helpful Table of Contents for those Journals (with links to the relevant issue) can be found on the MUFON Forum.
I have myself come across some useful articles e.g. there are two that relate to an important discussion about so-called ‘abduction’ experiences by veteran researcher John Spencer in the September and October issues of 1989. They are worth reading.
It’s great to see some of the old printed UFO journals from the US, acquired mainly through group-subscription, are now available online.