Taken from Ljubliana's Summer School on Semantic Web '05. More lectures available on http://videolectures.net
A lecture on applications of document summarization for generating semantic information in the form of graphs representing a given relationship on the text set.
Learning Semantic Sub-graphs for Document Summarization, Marko Grobelnik
Information Extraction Lecture
Information extraction, Ronen Feldman
And here's one that I made: a mind map of the above lecture: