There are A LOT of references available on this forum and similar others. The basics: Life Everlasting and Freedom of the Sons of God, I believed published in mid-60's was the cornerstone if my memory serves me correctly. Fred Franz, the obvious writer of the book promotes his chronology with the "6000 years of human existence" starting in 4026 BCE and ending in the momentous year of 1975 AD. 1975 was touted as a year of "tremendous probability" and people, particularly Franz and his chronies like a couple of DO's started revving up the brethren. The ORG can say they never said it, but, like a retired person looking at their account statements from Lehman Brothers going up and up with no end in sight (prior to its collapse), they did not question what was being said. No real cautionary statements. Yes, a cursory comment here or there, "not serving with a date in mind" and all that, but nothing to undermine the rhetoric. I mean, why would they? The ORG was growing leaps and bounds. The truth book comes out in the late 60's and people are being baptized in 6 months or else! That's right! "Don't waste your time on people who expect to study more than six months!" was the mantra in many congregations. There is no time to waste!
Having lived through it...having been baptized as a result of the fervor and extremely fanatical parents close to 1975, it was an event, not just an article. The expectation that Jehovah would soon wipe out every non-Witness was palpable!