1. Exponential lower bounds for the number of Skolem and extremal Langford sequences;Abrham;Ars. Combinat.,1986
2. Sequentially additive graphs;Bange;Discrete Math.,1983
3. I. Cahit, Another formulation of the graceful tree conjecture, Research report CORR 80-47, Dept C&O, University of Waterloo, Ontario, Canada, 1980
4. On graceful trees;Cahit;Bull. Inst. Combin. Appl.,1994
5. How to gracefully number certain symmetric trees;Gabow;SIGACT News 7,1975