@ARTICLE{DasPauSal_j1993_c, author = {J{\"u}rgen~Dassow and Gheorghe~P\u{a}un and Arto~Salomaa}, title = {On thinness and slenderness of {L} languages}, journal = beatcs, year = 1993, volume = 49, number = {}, pages = {152--158} }