The Two Circles of Taiji
This is always the first video that I refer others to if I am asked about Chen Style Taijiquan Practical Method. As I searched for the YouTube link for this video today, I found one additional site that I hadn't been to before.
https://www.epsb.net/~jchen
It's an early site by Master Chen.
Source: https://practicalmethod.com/?p=12007