1. Georg Gottlob, Zoltán Miklós and Thomas Schwentick.
    Generalized hypertree decompositions: NP-hardness and tractable variants.
    J. ACM 56(6), 2009.
    URL, DOI BibTeX

    @article{DBLP:journals/jacm/GottlobMS09,
    	author = "Georg Gottlob and Zolt{\'{a}}n Mikl{\'{o}}s and Thomas Schwentick",
    	title = "Generalized hypertree decompositions: NP-hardness and tractable variants",
    	journal = "J. {ACM}",
    	year = 2009,
    	volume = 56,
    	number = 6,
    	url = "http://doi.acm.org/10.1145/1568318.1568320",
    	doi = "10.1145/1568318.1568320",
    	timestamp = "Tue, 18 Nov 2014 21:31:20 +0100",
    	biburl = "http://dblp.uni-trier.de/rec/bib/journals/jacm/GottlobMS09",
    	bibsource = "dblp computer science bibliography, http://dblp.org"
    }
    

  1. Mikolaj Bojanczyk, Anca Muscholl, Thomas Schwentick and Luc Segoufin.
    Two-variable logic on data trees and XML reasoning.
    J. ACM 56(3), 2009.
    URL, DOI BibTeX

    @article{DBLP:journals/jacm/BojanczykMSS09,
    	author = "Mikolaj Bojanczyk and Anca Muscholl and Thomas Schwentick and Luc Segoufin",
    	title = "Two-variable logic on data trees and {XML} reasoning",
    	journal = "J. {ACM}",
    	year = 2009,
    	volume = 56,
    	number = 3,
    	url = "http://doi.acm.org/10.1145/1516512.1516515",
    	doi = "10.1145/1516512.1516515",
    	timestamp = "Tue, 18 Nov 2014 21:31:15 +0100",
    	biburl = "http://dblp.uni-trier.de/rec/bib/journals/jacm/BojanczykMSS09",
    	bibsource = "dblp computer science bibliography, http://dblp.org"
    }