“…An algorithm for rebalancing after a deletion appeared several years later, in a technical report by a different author [7]; deletion requires O(log n) rotations rather than O (1). For all existing forms of balanced trees, of which there are many [3,4,5,9,10,12,13,16], deletion is at least a little more complicated than insertion, although for some kinds of balanced search trees, notably red-black trees [9] and the recently introduced rank-balanced trees [10], rebalancing after a deletion can be done in O(1) rotations. Many textbooks describe algorithms for insertion but not deletion.…”