Some of these info were passed downed by my parents, aunts and uncles over the years. A few years back, one of my uncles went back to China and got a chart - Giai Thu Ho Quach - which confirmed most of what was passed on to us, plus few more details.
There are still lots of older people from my parents' villages, who we can ask. If you know where about in Vietnam or China your family/ies used to live in, I would start asking these elders. These days, they are scattered around in places like LA, San Jose, San Francisco, Sydney, Toronto and obviously in China.
My cousins recently ran into people who previously went to school with my father and uncle, back in China, for instant, and they were able to tell us some details about the older generations and others who knew my families. We just have to filter through some of the myths/legends and find the facts.
Good luck with your search. If you do come across anything that you can share, please let me know.