Name two other sources shaw used for this play and explain how he used a specific element from each source.

Shaw has Alexander Melville Bell was the source for his character Higgins. Bell invented the theatrical concept known as "Visible Speech". Shaw draws on this concept through his character Eliza Doolittle, in which both sight and sound, the main elements of Visible Speech, are seen through her inner and outer transformations.

I believe the other source to be Romanticism. Shaw seems to purposely challenge the idea of romance throughout the play, for example, by creating characters which are boring and consumed with irrelevancies. This idea also goes with Shaw's twisted concept of the myth/fairy tale.