At Pontifications, Al Kimel has
posted two lengthy excerpts from Joseph Gill, SJ's fascinating book
The Council of Florence (1982). The passages recount the course of discussion on the
filioque clause ("and the Son") inserted into the Nicene-Constantinopolitan Creed by the Catholic Church during the Middle Ages. Next to that of papal primacy, the
filioque is probably the most vexed issue dividing the Catholic and Orthodox churches from each other. Florence's treatment of it was important because that council effected a reunion of the churches that, while real, was short-lived because it was never "received" by most Orthodox and ended up being formally repudiated by Orthodox synods before much time passed. I don't know of any exposition of Florence's discussions that even approach Gill's for thoroughness and accuracy.
Like most worthy books in my fields of interest, Gill's is currently out of print and was quite expensive when it was in print. I've only read it in a library where I had no borrowing rights. But it is essential reading for those who, like Kimel,me, and many others, hope to see progress toward breaking the impasse.