Below is a list of sources that contain information about Runska (the list is constantly being updated):
Ariste, Paul. 1940. Om lånorden i runödialekten. [About loanwords in Ruhnu Swedish] Tartu: Akadeemiline Rootsi-Eesti Selts.
Lagman, Edvin (ed.). 1990. En bok om Estlands svenskar. 3A: Estlandssvenskarnas språkförhållanden. [A Book about the Estonian Swedes. 3A: The Language Situation of the Estonian Swedes] Stockholm: Kulturföreningen Svenska odlingens vänner.
Vendell, Herman Albert. 1882. Runömålet: ljud- ock formlära samt ordbok[The Ruhnu language: phonology and morphology, as well as a dictionary] (Nyare Bidrag till Kännedom Om de Svenska Landsmålen Ock Svenskt Folkliv 2:3). Stockholm: Svenska odlingens vänner.
For an overview of various journal articles on Ruhnu Swedish and Estonian Swedish see the presentation slides by Henrik Rosenkvist.