The book at the link below will give you a very good place to start if you desire to do more reading and research about the Oneness movement in the 20th century:
https://www.amazon.com/Their-Story-2.../dp/B004A90BEM
This as well:
https://www.amazon.com/History-Chris.../dp/B004P8JIAG
For a scholar's take, this book has two chapters devoted to early Oneness Pentecostals, Andrew Urshan and Garfield Haywood:
https://www.amazon.com/Thinking-Spir.../dp/0253216036