Of course I already have some literature, for example
Zwischen Isolation und Sprachkontakt: Der romanische Wortschatz der Vorarlberger Walser: http://www.jstor.org/stable/40503977
Alessio Boattini, Clio Griso & Davide Pettener. Are ethnic minorities synonymous for genetic isolates? Journal of Anthropological Sciences. Vol. 89 (2011), pp. 161-173.
Mathieu Petite. A new perspective on the Walser community.
But I can not find an article with the results of the research.