+
+@article{ tarjan:applpc,
+ author = {Robert Endre Tarjan},
+ title = {Applications of Path Compression on Balanced Trees},
+ journal = {Journal of the ACM},
+ volume = {26},
+ number = {4},
+ year = {1979},
+ issn = {0004-5411},
+ pages = {690--715},
+ doi = {http://doi.acm.org/10.1145/322154.322161},
+}
+
+@article{ kostochka:lbh,
+ title={{Lower bound of the Hadwiger number of graphs by their average degree}},
+ author={Kostochka, A. V.},
+ journal={Combinatorica},
+ volume={4},
+ number={4},
+ pages={307--316},
+ year={1984},
+}
+
+@article{ thomason:efc,
+ title={{An extremal function for contractions of graphs}},
+ author={Thomason, A.},
+ journal={Mathematical proceedings of the Cambridge Philosophical Society},
+ volume={95},
+ number={2},
+ pages={261--265},
+ year={1984},
+ publisher={Cambridge University Press}
+}