+
+@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},
+ publisher={Springer}
+}
+
+@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}
+}