# Reference 0. []() 0. [6.851: Advanced Data Structures (Spring'21)](https://courses.csail.mit.edu/6.851/spring21/) 0. [An Efficient Representation for Sparse Sets](http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.30.7319&rep=rep1&type=pdf) 0. [Red-black tree implementation notes](http://jstimpfle.de/blah/rbtree/main.html)