@misc {IOPORT.70211495,
    author       = {Choffrut, Christian and Duboc, Christine},
    title        = {A star-height problem in free monoids with partial communications},
    howpublished = {ICALP, 190-201 (1987).},
    year         = {1987},
    doi          = {10.1007/3-540-18088-5_15},
    identifier   = {70211495},
}