2 The John Knopfmacher Centre for Applicable Analysis and Number Theory [Johannesburg]
q-binary search trees are obtained from words, equipped with a geometric distribution instead of permutations. The average and variance of the heighth computated, based on random words of length n, as well as a Gaussian limit law.
Hosam M. Mahmoud, 2003, One-sided variations on binary search trees, Annals of the Institute of Statistical Mathematics, 55, 4, pp. 885-900, 10.1007/bf02523399.