Person: Seidel, Jaap
Jaap Seidel was a Dutch mathematician who who worked in geometry and graph theory.
Mathematical Profile (Excerpt):
 At an early age already, Jaap had experience in what is now called Networking.
 When it became clear that the closure was not going to be a short one, Seidel, who had continued his studies there up to that point, now transferred to the Free University of Amsterdam where he was strongly influenced by Johannes Haantjes.
 Soon Seidel found an opportunity to escape from the Germans and was able to return to the Netherlands where he remained in hiding for the rest of the war.
 From March to July 1946, Seidel taught engineering at a secondary training school in Amsterdam, then from September 1946 to September 1950 he taught at the prestigious Vossius Gymnasium in Amsterdam.
 Haantjes had moved from Amsterdam to Leiden, so it was natural for Seidel to submit his doctoral studied there.
 Haantjes and Seidel announced the results in the paper The congruence order of the elliptic plane (1947).
 Seidel published full proof in his 71 page thesis published in 1948.
 Seidel had been put in charge of the Entertainment Committee for the International Congresses of Mathematicians held in Amsterdam in September 1954.
 In the spring of 1955 Seidel was given leave to study with Van der Ven in Rome, an unusual privilege for someone in his position.
 Johannes Haantjes became ill in 1955 (he died in the following year) and Seidel was asked to give some of his courses at Leiden.
 All these conferences published proceedings and Seidel's contribution was published in each.
 We end this biography with two tributes to Seidel.
 Many mathematicians, especially young ones, were influenced by Jaap.
 Jaap's work makes connections with several branches in mathematics, and he had struck friendships with mathematicians all over the world.
Born 19 August 1919, The Hague, The Netherlands. Died 8 May 2001, Eindhoven, The Netherlands.
View full biography at MacTutor
Tags relevant for this person:
Origin Netherlands
Thank you to the contributors under CC BYSA 4.0!
 Github:

 nonGithub:
 @JJO'Connor
 @EFRobertson
References
Adapted from other CC BYSA 4.0 Sources:
 Oâ€™Connor, John J; Robertson, Edmund F: MacTutor History of Mathematics Archive