If you read french, it exists a very good french revue (a big revue).
Its name is " ICARE - Revue de l'aviation française " n° 160 - Tome 2 ".
This tome talk about Escadrille Lafayette and a big chapter concerns
Raoul Lufbery and particularly his life before WW1 and his meet with Marc Pourpe.
A very very good revue.
Ludo