Links to studies about tactics and puzzle solving

A few links to external puzzle sites.

chesscup.org/
Free puzzle rush / Source : Lichess puzzles

blitztactics.com/
Source : Lichess puzzles

www.chesspuzzle.net/
A lot of puzzles from various sources

chesstempo.com/
Maybe the best puzzle site ?

2 studies about common endgame tactics

From my studies:
ARTISTIC CHESS

Progressive puzzles
40 chapters

With a description how to solve chess puzzles.
With a description of the 5 most common chess tactics.
With a full description of all tactical motifs (56)
chessfox.com/tactics/

Check out this puzzle study created by me! [Da_One is my first acc]

A lot of chesspuzzles can be found here.
http://wtharvey.com/