@article{1256049900,
author = {Dyer, Micheal N.},
title = {Homotopy trees: Essential height and roots},
journal = {Illinois J. Math.},
volume = {20},
number = {4},
year = {1976},
pages = { 306-313},
language = {en},
url = {http://dml.mathdoc.fr/item/1256049900}
}
Dyer, Micheal N. Homotopy trees: Essential height and roots. Illinois J. Math., Tome 20 (1976) no. 4, pp. 306-313. http://gdmltest.u-ga.fr/item/1256049900/