Christian Dax Felix Klaedtke Martin Lange On Regular Temporal Logics with Past, . 175-187 2009 ICALP (2) http://dx.doi.org/10.1007/978-3-642-02930-1_15 conf/icalp/2009-2 db/conf/icalp/icalp2009-2.html#DaxKL09