PP-2005-27: Niekus, Joop (2005) Brouwer's incomplete objects. [Report]
PP-2002-05: Niekus, Joop (2002) Individual Choice Sequences in the Work of L.E.J.Brouwer. [Report]
PP-2017-02: Niekus, Joop (2017) What is a choice sequence? How a solution of Troelstra's paradox shows the way to an answer to this question. [Pre-print]