Also, in my 1929 Encyclopedia Britannica, is the following excerpt:

"In the folklore of Scotland his name is associated with numerous fragments of verse of a gnomic and prophetic character. The romance of Thomas and the elf-queen was attributed to Erceldoune by Robert Mannyng de Brunne, but the earliest text, in the Auchinleck ms. in the Advocates' library, Edinburgh, is in a dialect showing southern forms, and dates from the beginning of the 14th century. It may be based on a geniune work of Thomas, a version by him of the widely diffused Tristan Saga. The most widely accepted opinion is that it is a translation of a French origional."

I am unaware of several things here...Robert Mannyng de Brunne, Auchinleck ms., and the Advocates' library. Anyone out there with a clue?ttr