I don't know why the above text is not parsed, I get the replies:

>Error 27: Entity 'deg' not defined Line: 1, column: 123
>Fatal Error 23: EntityRef: expecting ';' Line: 24, column: 336

but there is no deg in line 1.

(I fixed the above post. The main problem was using an `` without a matching ``. This tends to cause mysterious error messages. - John Baez)