Hi Morgain. =)
Most of the info I posted in the "Extroverted Introvert" thread about Jung's definitions is stuff I've cobbled together from whatever cognitive function descriptions I could get my hands on, but also from reading the abstracts of Jung's "Psychological Types" (they're really easy to find online if you ever want to read them yourself). I'm not quite sure where I first heard about Eysenck's theory, I think it might have been on one of the MBTI forums, maybe even on this one somewhere (though I have no idea where). What I posted was pretty much everything I know about it though. =/