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 author       = {Alfred Aho},
 year         = {1968},
 title        = {Indexed Grammars -- An Extension of Context-Free Grammars},
 journal      = {Journal of the {ACM}},
 volume       = {15},
 number       = {4},
 pages        = {647--671},
 doi          = {10.1145/321479.321488},
)
@article(Aho-Ullman72a,
 author       = {Alfred Aho and Jeffrey Ullman},
 year         = {1972},
 title        = {Translations on a Context Free Grammar},
 journal      = {Information and Control},
 volume       = {19},
 number       = {5},
 pages        = {439--475},
 doi          = {10.1016/S0019-9958(71)90706-6},
)
@article(Anisimov71a,
 author       = {Anatoly Anisimov},
 year         = {1971},
 title        = {Group languages},
 journal      = {Cybernetics},
 volume       = {7},
 pages        = {594--601},
 doi          = {10.1007/BF01071030},
)
@article(Asveld77a,
 author       = {Peter Asveld},
 year         = {1977},
 title        = {Controlled iteration grammars and full hyper-{AFL}'s},
 journal      = {Information and Control},
 volume       = {34},
 number       = {3},
 pages        = {248--269},
 doi          = {10.1016/S0019-9958(77)90308-4},
)
@inproceedings(Ciobanu-Elder19a,
 author       = {Laura Ciobanu and Murray Elder},
 year         = {2019},
 title        = {Solutions Sets to Systems of Equations in Hyperbolic Groups Are {EDT0L} in {PSPACE}},
 booktitle    = {Proc.\ 46th International Colloquium on Automata, Languages, and Programming ({ICALP 2019})},
 series       = {Leibniz International Proceedings in Informatics ({LIPIcs})},
 volume       = {132},
 publisher    = {Schloss Dagstuhl--Leibniz-Zentrum f{\"u}r Informatik},
 pages        = {110:1--110:15},
 doi          = {10.4230/LIPIcs.ICALP.2019.110},
)
@article(Ciobanu-Elder-Ferov18a,
 author       = {Laura Ciobanu and Murray Elder and Michal Ferov},
 year         = {2018},
 title        = {Applications of {L} systems to group theory},
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 volume       = {28},
 number       = {2},
 pages        = {309--329},
 doi          = {10.1142/S0218196718500145},
)
@inproceedings(Denkinger16a,
 author       = {Tobias Denkinger},
 year         = {2016},
 title        = {An Automata Characterisation for Multiple Context-Free Languages},
 booktitle    = {Proc.\ International Conference on Developments in Language Theory ({DLT 2016})},
 series       = {Lecture Notes in Computer Science},
 volume       = {9840},
 publisher    = {Springer},
 pages        = {138--150},
 doi          = {10.1007/978-3-662-53132-7_12},
)
@inbook(Drewes-Kreowski-Habel97a,
 author       = {Frank Drewes and Hans-J{\"o}rg Kreowski and Annegret Habel},
 year         = {1997},
 title        = {Hyperedge Replacement Graph Grammars},
 pages        = {95--162},
 publisher    = {World Scientific},
 doi          = {10.1142/9789812384720_0002},
)
@article(Ehrenfeucht-Rozenberg77a,
 author       = {Andrzej Ehrenfeucht and Grzegorz Rozenberg},
 year         = {1977},
 title        = {On some context-free languages that are not deterministic {ET0L} languages},
 journal      = {R.A.I.R.O. Informatique th{\'e}orique},
 volume       = {11},
 number       = {4},
 pages        = {273--291},
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)
@article(Engelfriet-Heyker91a,
 author       = {Joost Engelfriet and Linda Heyker},
 year         = {1991},
 title        = {The string generating power of context-free hypergraph grammars},
 journal      = {Journal of Computer and System Sciences},
 volume       = {43},
 number       = {2},
 pages        = {328--360},
 doi          = {10.1016/0022-0000(91)90018-Z},
)
@article(Gilman-Kropholler-Schleimer18a,
 author       = {Robert Gilman and Robert Kropholler and Saul Schleimer},
 year         = {2018},
 title        = {Groups whose word problems are not semilinear},
 journal      = {Groups Complexity Cryptology},
 volume       = {10},
 number       = {2},
 pages        = {53--62},
 doi          = {10.1515/gcc-2018-0010},
)
@misc(Gilman-Shapiro98a,
 author       = {Robert Gilman and Michael Shapiro},
 year         = {1998},
 title        = {On groups whose word problem is solved by a nested stack automaton},
 url          = {https://arxiv.org/abs/math/9812028},
)
@book(Habel92b,
 author       = {Annegret Habel},
 year         = {1992},
 title        = {Hyperedge Replacement: Grammars and Languages},
 series       = {Lecture Notes in Computer Science},
 volume       = {643},
 publisher    = {Springer},
 doi          = {10.1007/BFb0013875},
)
@book(Hatcher02a,
 author       = {Allen Hatcher},
 year         = {2002},
 title        = {Algebraic Topology},
 publisher    = {Cambridge University Press},
)
@article(Herbst-Thomas93a,
 author       = {Thomas Herbst and Richard Thomas},
 year         = {1993},
 title        = {Group presentations, formal languages and characterizations of one-counter groups},
 journal      = {Theoretical Computer Science},
 volume       = {112},
 number       = {2},
 pages        = {187--213},
 doi          = {10.1016/0304-3975(93)90018-O},
)
@article(Ho18a,
 author       = {Meng-Che Ho},
 year         = {2018},
 title        = {The word problem of {$\mathbb{Z}^n$} is a multiple context-free language},
 journal      = {Groups Complexity Cryptology},
 volume       = {10},
 number       = {1},
 pages        = {9--15},
 doi          = {10.1515/gcc-2018-0003},
)
@book(Hopcroft-Motwani-Ullman06a,
 author       = {John Hopcroft and Rajeev Motwani and Jeffrey Ullman},
 year         = {2006},
 title        = {Introduction to Automata Theory, Languages, and Computation},
 edition      = {3rd ed.},
 publisher    = {Addison-Wesley},
)
@inbook(Kreowski92a,
 author       = {Hans-J{\"o}rg Kreowski},
 year         = {1992},
 title        = {Parallel Hyperedge Replacement},
 pages        = {271--282},
 publisher    = {Springer},
 doi          = {10.1007/978-3-642-58117-5_17},
)
@inproceedings(Kreowski93a,
 author       = {Hans-J{\"o}rg Kreowski},
 year         = {1993},
 title        = {Five facets of hyperedge replacement beyond context-freeness},
 booktitle    = {Proc.\ 9th International Conference on Fundamentals of Computation Theory ({FCT 1993})},
 series       = {Lecture Notes in Computer Science},
 volume       = {710},
 publisher    = {Springer},
 pages        = {69--86},
 doi          = {10.1007/3-540-57163-9_5},
)
@article(Kropholler-Spriano19a,
 author       = {Robert Kropholler and Davide Spriano},
 year         = {2019},
 title        = {Closure properties in the class of multiple context-free groups},
 journal      = {Groups Complexity Cryptology},
 volume       = {11},
 number       = {1},
 pages        = {1--15},
 doi          = {10.1515/gcc-2019-2004},
)
@book(Massey77a,
 author       = {William Massey},
 year         = {1977},
 title        = {Algebraic Topology: An Introduction},
 series       = {Graduate Texts in Mathematics},
 volume       = {56},
 publisher    = {Springer},
)
@article(Muller-Schupp83a,
 author       = {David Muller and Paul Schupp},
 year         = {1983},
 title        = {Groups, the Theory of Ends, and Context-Free Languages},
 journal      = {Journal of Computer and System Sciences},
 volume       = {26},
 number       = {3},
 pages        = {295--310},
 doi          = {10.1016/0022-0000(83)90003-X},
)
@article(Nielsen75a,
 author       = {Mogens Nielsen},
 year         = {1975},
 title        = {{EOL} systems with control devices},
 journal      = {Acta Informatica},
 volume       = {4},
 pages        = {373--386},
 doi          = {10.1007/BF00289618},
)
@article(Nishida-Seki00a,
 author       = {Taishin Nishida and Shigeko Seki},
 year         = {2000},
 title        = {Grouped partial {ET0L} systems and parallel multiple context-free grammars},
 journal      = {Theoretical Computer Science},
 volume       = {246},
 number       = {1--2},
 pages        = {131--150},
 doi          = {10.1016/S0304-3975(99)00076-6},
)
@article(Novikov55a,
 author       = {Pyotr Novikov},
 year         = {1955},
 title        = {{\"U}ber die algorithmische Unentscheidbarkeit des Wortproblems in der Gruppentheorie},
 journal      = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
 volume       = {44},
 pages        = {1--143},
)
@article(Parikh66a,
 author       = {Rohit Parikh},
 year         = {1966},
 title        = {On Context-Free Languages},
 journal      = {Journal of the {ACM}},
 volume       = {13},
 number       = {4},
 pages        = {570--581},
 doi          = {10.1145/321356.321364},
)
@book(Rozenberg-Salomaa80a,
 author       = {Grzegorz Rozenberg and Arto Salomaa},
 year         = {1980},
 title        = {The Mathematical Theory of {L} Systems},
 series       = {Pure and Applied Mathematics},
 volume       = {90},
 publisher    = {Academic Press},
)
@article(Salvati15a,
 author       = {Sylvain Salvati},
 year         = {2015},
 title        = {MIX is a 2-MCFL and the word problem in {$\mathbb{Z}^2$} is captured by the IO and the OI hierarchies},
 journal      = {Journal of Computer and System Sciences},
 volume       = {81},
 number       = {7},
 pages        = {1252--1277},
 doi          = {10.1016/j.jcss.2015.03.004},
)
@article(Seki-Matsumura-Fujii-Kasami91a,
 author       = {Hiroyuki Seki and Takashi Matsumura and Mamoru Fujii and Tadao Kasami},
 year         = {1991},
 title        = {On multiple context-free grammars},
 journal      = {Theoretical Computer Science},
 volume       = {88},
 number       = {2},
 pages        = {191--229},
 doi          = {10.1016/0304-3975(91)90374-B},
)
@inproceedings(Shanker-Weir-Joshi87a,
 author       = {Vijay Shanker and David Weir and Aravind Joshi},
 year         = {1987},
 title        = {Characterizing structural descriptions produced by various grammatical formalisms},
 booktitle    = {Proc.\ 25th Annual Meeting on Association for Computational Linguistics ({ACL '87})},
 publisher    = {Association for Computational Linguistics},
 pages        = {104--111},
 doi          = {10.3115/981175.981190},
)
@inproceedings(Weir92a,
 author       = {David Weir},
 year         = {1992},
 title        = {Linear context-free rewriting systems and deterministic tree-walking transducers},
 booktitle    = {Proc.\ 30th Annual Meeting of the Association for Computational Linguistics},
 publisher    = {Association for Computational Linguistics},
 pages        = {136--143},
 doi          = {10.3115/981967.981985},
)