Can you explain "Oneness Pentecostalism?"?

Fairly early in the Pentecostal revival some participants believed they had gotten a revelation that God is one person who plays three different roles (historically known as Sabellianism or modalism). To them, salvation is not possible apart from baptism in Jesus name only. They believe that if anything else is said while you are baptized you are not saved. They are also quite legalistic. The women do not cut their hair (although some get around this by burning it with a curling iron) and they do not wear jewelry. They do not own televisions. Any Pentecostal group which has the name "Apostolic" is sure to be Oneness. The largest Oneness denomination at this time is the United Pentecostal Church. The vast majority of Pentecostals are trinitarians who do not think the exact words spoken over the one baptized are crucial to one's salvation and who do not embrace the legalisms that Oneness Pentecostals do.