@article{10_4064_cm_74_2_321_328,
     author = {Franz Lehner},
     title = {Free operators with operator coefficients},
     journal = {Colloquium Mathematicum},
     pages = {321--328},
     publisher = {mathdoc},
     volume = {74},
     number = {2},
     year = {1997},
     doi = {10.4064/cm-74-2-321-328},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/cm-74-2-321-328/}
}