Leszek Gasieniec Jesper Jansson Andrzej Lingas Anna Östlin On the Complexity of Constructing Evolutionary Trees. 183-197 1999 3 J. Comb. Optim. 2-3 db/journals/jco/jco3.html#GasieniecJLO99 http://dx.doi.org/10.1023/A:1009833626004