@inproceedings{mfcs15,
	author = {L. Aceto and
                  Della Monica, D. and
                  I. F\'abregas and
                  A. Ing\'olfsd\'ottir},
	title = {When are prime formulae characteristic?},
        booktitle = {Proc. of the 40th International Symposium
                     on Mathematical Foundations of Computer
                     Science (MFCS)---Part I},
        series = {LNCS},
        volume = {9234},
        pages = {76--88},
        doi = {10.1007/978-3-662-48057-1_6},
        publisher = {Springer-Verlag Berlin Heidelberg},
        editor = {Giuseppe F. Italiano and
                  Giovanni Pighizzini and
                  Donald Sannella},
        year = {2015}
}