@article{Bertoni&Massazza&Sabadini:1992,
	key = "Bertoni, Massazza, and Sabadini 1992",
     author = "Bertoni, A. and Massazza, P. and Sabadini, N.",
     title = "Holonomic generating functions and context free languages",
     journal = IJFCS,
     volume = 3,
     year = 1992,
     pages = "181-191"}

@inproceedings{Salomaa:1993,
	key = "Salomaa 1993",
     author = "Salomaa, A.",
     title = "Pattern languages:  problems of decidability and generation",
     booktitle = FCT93,
     series = LNICS,
     volume = 710,
     publisher = SV,
     year = 1993,
     editor = "Z. {\'Esik}",
     pages = "121-132"}

@inproceedings{Mignosi&Seebold:1993a,
	key = "Mignosi and {S\'e\'ebold} 1993a",
     author = "Mignosi, F. and {S\'e\'ebold}, P.",
     title = "If a {D0L} language is $k$-power free then it is circular",
     booktitle = ICALP93,
     series = LNICS,
     volume = 700,
     year = "{\noopsort{1993a}}1993",
     editor = "A. Lingas and R. Karlsson and S. Carlsson",
     pages = "507-518"}

@inproceedings{Jiang&Salomaa&Salomaa&Yu:1993,
	key = "Jiang, Salomaa, Salomaa, and Yu 1993",
     author = "Jiang, T. and Salomaa, A. and Salomaa, K. and Yu, S.", 
     title = "Inclusion is undecidable for pattern languages",
     booktitle = ICALP93,
     series = LNICS,
     volume = 700,
     year = 1993,
     editor = "A. Lingas and R. Karlsson and S. Carlsson",
     pages = "301-312"}

@article{Autebert&Flajolet&Gabarro:1987,
	key = "Autebert, Flajolet, and {Gabarr\'o} 1987",
     author = "Autebert, J. and Flajolet, P. and {Gabarr\'o}, J.",    
     title = "Prefixes of infinite words and ambiguous context-free languages",
     journal = IPL,
     volume = 25,
     year = 1987,
     pages = "211-216",
     comment = "checked"}

@articlenovol{Kosa:1987,
	key = "{K\'osa} 1987",
     author = "{K\'osa}, M.",
     title = "Problems from the border of theoretical computer science and the theory
of numbers",
     journal = BEATCS,
     number = 32,
     year = 1987,
     pages = "331-333"}

@articlenovol{Seebold:1988,
	key = "{S\'e\'ebold} 1988",
     author = "{S\'e\'ebold}, P.",
     title = "An effective solution to the {D0L} periodicity problem
in the binary case",
     journal = BEATCS,
     volume = 36,
     year = 1988,
     pages = "137-151"}

@article{Honkala:1993,
	key = "Honkala 1993",
     author = "Honkala, J.",
     title = "On {D0L} systems with immigration",
     journal = TCS,
     volume = 120,   
     year = 1993,
     pages = "229-245",
     comment = "checked"}

@article{Ehrenfeucht&Rozenberg&Skyum:1976,
	key = "Ehrenfeucht, Rozenberg, and Skyum 1976",
     author = "Ehrenfeucht, A. and Rozenberg, G. and Skyum, S.",
     title = "A relationship between {ET0L} and {EDT0L} languages",
     journal = TCS,
     volume = 1,
     year = 1976,
     pages = "325-330",
     comment = "checked"}

@article{Szilard&Quinton:1979,
	key = "Szilard and Quinton 1979",
     author = "Szilard, A. L. and Quinton, R. E.",
     title = "An interpretation for {D0L} systems by computer graphics",     
     journal = TST,
     volume = 4,
     year = 1979,
     pages = "8-13"}

@article{Dietrich&Gronau&Steffen:1980,
	key = "Dietrich, Gronau, and Steffen 1980",
     author = "Dietrich, H. and Gronau, O. F. and Steffen, G.",
     title = "A problem of {L} system interest",
     journal = MNACH,
     volume = 99,
     year = 1980,
     pages = "29-31"}

@article{Karhumaki&Linna:1983,
	key = "{Karhum\"aki} and Linna 1983",
     author = "{Karhum\"aki}, J. and Linna, M.",
     title = "A note on morphic characterization of languages",
     journal = DAM,
     volume = 5,
     year = 1983,
     pages = "243-246"}

@inproceedings{deLuca&Restivo:1984,
	key = "de Luca and Restivo 1984",
        author = "Luca, A. de and Restivo, A.",
        title = "Representations of integers and language theory",
        booktitle = MFCS84,
        year = 1984,
        pages = "407-415",
        series = LNICS,
	editor = "M. P. Chytil and V. Koubek",
	publisher = SV,
        volume = 176}

@incollection{Chomsky&Schutzenberger:1963,
	key = "Chomsky and {Sch\"utzenberger} 1963",
        author = "Chomsky, N. and {Sch\"utzenberger}, M. P.",
        title = "The algebraic theory of context-free languages",
        booktitle = "Computer Programming and Formal Systems",
        year = 1963,
	editor = "P. Braffort and D. Hirschberg",
        publisher = "North Holland",
        address = "Amsterdam",
        pages = "118-161"}

@book{Shyr:1991,
	key = "Shyr 1991",
	author = "H. J. Shyr",
	title = "Lecture Notes:  Free Monoids and Languages",
	publisher = "Hon Min Book Company",
	address = "Taiwan",
	year = 1991}

@article{Berstel:1986a,
	key = "Berstel 1986a",
	author = "J. Berstel",
	title = "Every iterated morphism yields a {co-CFL}",
	journal = IPL,
	volume = 22,
	year = "{\noopsort{1986a}}1986",
	pages = "7-9",
	comment = "checked"}

@incollection{Berstel:1973,
	key = "Berstel 1973",
	author = "J. Berstel",
	title = "Sur la {densit\'e} asymptotique de langages formels",
	booktitle = ICALP72,
	year = 1973,
	editor = "M. Nivat",
	publisher = "North-Holland",
	pages = "345-358"}

@article{Autebert&Beauquier&Boasson&Nivat:1979,
	key = "Autebert, Beauqier, Boasson, and Nivat 1979",
	author = "J. M. Autebert and J. Beauquier and L. Boasson and M. Nivat",
	title = "Quelques {probl\`emes} ouverts en {th\'eorie} des 
langages {alg\'ebriques}",
	journal = RAIRO,
	volume = 13,
	year = 1979,
	pages = "363-379"}

@techreport{Myhill:1957,
	key = "Myhill 1957",
	author = "J. Myhill",
	title = "Finite automata and the representation of events",
	institution = "Wright Patterson Air Force Base",
	address = "Ohio",
	number = "WADD TR-57-624",
	year = 1957}

@article{Nerode:1958,
	key = "Nerode 1958",
	author = "A. Nerode",
	title = "Linear automaton transformations",
	journal = PAMS,
	volume = 9,
	year = 1958,
	pages = "541-544"}

@article{Bar-Hillel&Perles&Shamir:1961,
	key = "Bar-Hillel, Perles, and Shamir 1961",
	author = "Y. Bar-Hillel and M. Perles and E. Shamir",
	title = "On formal properties of simple phrase structure
grammars",
	journal = ZPSK,
	volume = 14,
	year = 1961,
	pages = "143-172"}

@article{Chomsky:1956,
	key = "Chomsky 1956",
	author = "N. Chomsky",
	title = "Three models for the description of language",
	journal = IRE-IT,
	volume = 2,
	year = 1956,
	pages = "113-124"}

@article{Chomsky:1959,
	key = "Chomsky 1959",
	author = "N. Chomsky",
	title = "On certain formal properties of grammars",
	journal = IC,
	volume = 2,
	year = 1959,
	pages = "137-167"}

@incollection{Oettinger:1961,
	key = "Oettinger 1961",
	author = "A. G. Oettinger",
	title = "Automatic syntactic analysis and the pushdown store",
	series = PSAM,
	booktitle = "Structure of Language and Its Mathematical Aspects",
	volume = 12,
	year = 1961,
	pages = "104-129"}

@incollection{Chomsky:1962,
	key = "Chomsky 1962",
	author = "N. Chomsky",
	title = "Context-free grammars and pushdown storage",
	booktitle = "Quarterly Progress Report No. 65",
	publisher = "MIT Research Lab. Elect.",
	address = "Cambridge, Mass.",
	year = 1962,
	pages = "187-194"}

@incollection{Evey:1963,
	key = "Evey 1963",
	author = "J. Evey",
	title = "Application of pushdown store machines",
	booktitle = "Proc. 1963 Fall Joint Computer Conference",
	year = 1963,
	pages = "215-227",
	publisher = "AFIPS Press"}

@article{Glaister&Shallit:1996,
	key = "Glaister and Shallit 1996",
	author = "I. Glaister and J. O. Shallit",
	title = "A lower bound technique for
the size of nondeterministic finite automata",
	journal = IPL,
	volume = 59,
	year = 1996,
	pages = "75-77"}

@incollection{Shallit:1999,
	key = "Shallit 1999",
	author = "J. O. Shallit",
	title = "Number theory and formal languages",
	booktitle = "Emerging Applications of Number Theory",
	editor = "D. A. Hejhal and J. Friedman and M. C. Gutzwiller and
A. M. Odlyzko",
	series = "IMA Volumes in Mathematics and Its Applications",
	volume = 109,
	publisher = SV,
	year = 1999,
	pages = "547-570"}