I came across this article today. It has good history and basics of sourdough:
http://www.independent.co.uk/life-style/food-and-drink/features/upper-crust-why-sourdough-is-the-best-bread-1669235.html [1]
Links[1] http://www.independent.co.uk/life-style/food-and-drink/features/upper-crust-why-sourdough-is-the-best-bread-1669235.html