1. Towards the Personal Communication Environment: Green Paper on Mobile and Personal Communications, European Commission DGXIII, April 27, 1994.
2. L.J. Stockmeyer, The set basis problem is NP-complete, IBM Report RC-5431, May, 1975.
3. The minimization of spatially multiplexed character sets;Gimbel;Commun. ACM,1974
4. L.T. Kou, C. K. Wong, A note on the set basis problem related to the compaction of character sets, IBM Report RC-5244, January, 1975.
5. An essay on prime implicants tables;Pyne;J. SIAM,1961