Jiong Qiu's summary of BBSO sigmoid observations
Other potentially relevent observations:
August 17, movie of erupting filament just to the right of sunspot seen above. This eruption was temporally linked with a flare of AR8668 and the additional eruption of the large polar crown filament due north of AR8668 (and its overlying streamer, see LASCO CME notes). Note that the filament in the movie (that is the one to the right of AR8668) has a forwards S shape.