Seiki Akama Yasunori Nagata Chikatoshi Yamada Three-Valued Temporal Logic <i>Q</i> <sub> <i>t</i> </sub> and Future Contingents. 215-231 2008 88 Studia Logica 2 http://dx.doi.org/10.1007/s11225-008-9102-0 db/journals/sLogica/sLogica88.html#AkamaNY08