Sébastien Ferenczi Charles Holton Luca Q. Zamboni Combinatorics of Three-Interval Exchanges. 567-578 2001 conf/icalp/2001 ICALP http://link.springer.de/link/service/series/0558/bibs/2076/20760567.htm db/conf/icalp/icalp2001.html#FerencziHZ01