What is the name of the sword in the stone?
They are the same and Vivian is the Lady of the Lake and it’s custodian when not in use. The “Story of Arthur” was not written down until Christianity came to Brittany and Wales. The story has existed in oral tradition all over Europe long before this. and good luck with that research, isn’t it like trying to see the picture a jigsaw puzzle makes with only 2/3 of the pieces. For a real mind bender, I’ve read some very scholarly literature on the subject that puts forth a very well founded and supported claim that there were several or at least 3 Arthurs and One pulled the Sword, one did something else all in separate lives and not in the same time period.