Theodorus Cornelis Louis Kok (born November 23, 1906 in The Hague; † May 28, 1999 there) was a well-known Dutch chess composer of endgame studies

Chess player
Like all talented young chess players, Kok wanted to become world champion. As a passionate attacker, he knew little about the end game. His father gave him 5 guilders for Berger's standard work. But he was also inspired by the book in memory of Weenink.

Chess composition
Between 1933 and 1938 Kok composed numerous endgame studies.

In his subsequently published monograph, which partly draws on earlier articles, they are grouped thematically: self-stalemate, stair maneuvers, intersection combinations for Nowotny and Plachutta, etc. But orthodox tasks, retroanalysis and self-checkmates are also represented.

After his book was published, he published under the pseudonyms Dorus Jansen, Kees Jansen and Gerrit Jansen. His contributions to the theory of queen and rook endgames are noteworthy.

A manuscript by Kok on the subject of The Black Lady in Zugzwang was found in Selman's estate, which ARVES published posthumously 50 years later.

Private
Kok studied mathematics and physics in Leyden. After graduating during the Great Depression, he sorted and distributed eggs in his father's wholesale company. He then worked as a bookmaker and statistician. From 1942 until his retirement he was an actuary at an insurance company in Utrecht and hardly composed any studies.

Literature
Theodorus Cornelis Louis Kok: Eindspelen en problems, The Hague, self-published, 1939.
Individual evidence
  Jan van Reek; Henk van Donk: Endgame study composing in The Netherlands and Flanders. Margraten, 1992, p. 41 ff ISBN 90-72939-12-3

Web link
Compositions by Theodorus Cornelis Louis Kok on the Schwalbe PDB server: 

20 chess problems can be found. 

Yet another chess problem: yacpdb.org can be found 114 chess problems: 22 chess problems and 92 endgame studies

Source: Germain Wikipedia

Kok´s famous endgame study:

Kok won with a brillant chess study (Ke3/Kg2) the first price in

Československý šach in August 1934 (598) 

   In the original publication, the solution only ends when the imprisoned black king is checkmated by the white knight. Since the white knight also has other ways to win after the black king has been imprisoned, the solution is dualistic right to the end. 

Correction:

A correction to the chess study is very easy: after the spectacular knight move 1.Na8!! Bd7 2.Nb6! h3 3.Bh2 Kh1! 4.Kf3 Kxh2 5.Kf2 the study must be finished and then this famous study is totally correct!  It goes without saying that after imprisoning the black king on h2 or h1, the two white knights can win against the black bishop in various ways. 
It is a great pity that this famous chess study by Kok is not published on Wikipedia or other internet forums because of the originally too long solution with dual.

Others: 72 endgame studies composed by Kok are selected on Dutch Website ARVES