Both those stars are in “Origami for beginners” by Vicente Palacios, ISBN 0486402843, and were designed by Francisco J. Caboblanco (pages 25 and 31). I love Palacios’ books and buyed all of them (second-hand), but they’re probably not good for beginners – very good for intermediary level, though.
The left star is made of 8 sheets of 7 cm Grimmhobby Senbazuru Chiyogami. The right star is made of 8 sheets of 7.5 cm washi Chiyogami.
The back of the stars is different, and nice too.
The two top stars are variations from a star by H. Azuma, in the book “Spiral origami” by Tomoko Fusè page 22, ISBN 8976221249 (korean? the editor seems to be Jong le Nara).
Searched all my books without success, so I’ve got no idea where I found the bottom star (references welcome).
Each star is made of one sheet of paper. The top left is made from 15 cm stars paper from ebay, the top right is 20 cm Folia Basics yellow, the bottom is 15 cm kami.
This star can be found in a Toyo small book in japanese, no idea what the title means, but ISBN 4902031010071, page 115. Again, no idea who the author is, if someone speaking japanese can tell me, I’ll update :)*
The star is folded from 16 sheets of 7 cm kami paper.
*Edit: once again, Michel Grand helped with identification of the author! As we can see on Origami House’website, it’s Yamaguchi Makoto, and the book is “Kirei na Origami”
(Beautiful Origami), number 6.