dissertation - use images from wikipedia - Gnu Free Doc License, CC License [on hold]

there is several images I would like to use in my thesis. The are under GFDL and Creative Commons licences (CC BY 1.0, CC BY-SA 3.0).

Q1: How should I properly reference them? Is it satisfactory to provide link only? Or do i have to put there some © symbol with some comment? Please show me some example.

Q2: I don't understand why these images are under two licenses (GFDL an CC). What logic is behind this?

Information about images: http://ift.tt/1J3bmJ3 http://ift.tt/1ByGEqo

Thanks