Perhaps this is what you mean by the filioque being "incomplete."
Yes, of course. It is summarize by St. Greogry Palamas when he says that "as regards His existence, the Spirit proceeds from the Father."
Although the Son and the Spirit are co-eternal with the Father, the unbegotten Father is still the cause and source of both the Son and the Spirit, in other words of Divinity, among other things.
"It is summarized by St. Greogry Palamas when he says that "as regards His existence, the Spirit proceeds from the Father.""
Which is pretty much exactly the Orthodox understanding of what the phrase "who proceeds from the Father" means, and why we cannot add the phrase "and the Son" in that context.
"I will try to find the reference to Photios's mention of unleavened bread."
Be sure to notify the folks at the Catholic Encyclopedia when you find it. I'm sure they would love to incorporate it into a subsequent revision, since they seem a bit chagrined at the fact that St. Photius specifically didn't challenge this particular Latin practice. :-)