1. On the existence of square roots in certain rings of power series;Brown;Math. Annalen,1965
2. Counting rooted planar maps;Liu;J. Math. Res. Expos.,1984
3. Enumeration of rooted nonseparable outerplanar maps;Liu;Acta Math. Appl. Sinica, Eng. Series,1989
4. On enumerating equations of planar maps;Liu;Chinese Adv. Math.,1989
5. Counting rooted triangulations;Tutte;Ann. Discrete Math.,1982