Atlas Linguistique de la Basse Bretagne :

The linguistic Atlas of Lower Brittany is the result of a linguistic atlas in the pipeline from 1910 to 1920 by the linguist Pierre Le Roux (linguist), and published for the first time in 1927. It consists of a collection of maps on the scale of lower Brittany, which lays out the different variations of the Breton language. The research was done with native speakers, in 77 communes. 600 words or phrases were checked. Atlas Linguistique de la Basse Bretagne, en 6 fascicules de 100 pages - Rééditions des Éditions Armoricaines