Hong-Chung Chen Yue-Li Wang An Efficient Algorithm for Generating Prüfer Codes from Labelled Trees. 97-105 2000 33 Theory Comput. Syst. 1 http://link.springer.de/link/service/journals/00224/bibs/0033001/00330097.html db/journals/mst/mst33.html#ChenW00