On the Complexity of Optimal Grammar-Based Compression
DCC '06 Proceedings of the Data Compression Conference
Generating all permutations by context-free grammars in Chomsky normal form
Theoretical Computer Science - Algebraic methods in language processing
Regular expressions: new results and open problems
Journal of Automata, Languages and Combinatorics
Generating all permutations by context-free grammars in Greibach normal form
Theoretical Computer Science
Generating all circular shifts by context-free grammars in Chomsky normal form
Journal of Automata, Languages and Combinatorics
IEEE Transactions on Information Theory
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Ellul, Krawetz, Shallit and Wang prove an exponential lower bound on the size of any context-free grammar generating the language of all permutations over some alphabet. We generalize their method and obtain exponential lower bounds for many other languages, among them the set of all squares of given length, and the set of all words containing each symbol at most twice.