Google is your friend. They are named after St. Dominic de Guzman ( who also happens to be the patron saint of Managua Nicaragua). Dozens of websites, this might be the best:
http://www.op.org/dsi/
They have a custom of not eating salted cod or herring and have tried to tax or ban it out of existence. Those nuclear silos were in fact large cod and herring repositories run by the Area 52 folks. (Neighbors to the more secretive Area 51).