@article {shemyakova:winkler:obstacles2:2007,
   author = {Shemyakova, E. and Winkler, F.},
   affiliation = {J. Kepler University Linz RISC-Linz A-4040 Linz Austria A-4040 Linz Austria},
   title = {Obstacles to factorization of partial differential operators into several factors},
   journal = {Programming and Computer Software},
   publisher = {MAIK Nauka/Interperiodica distributed exclusively by Springer Science+Business Media LLC.},
   issn = {0361-7688},
   keyword = {Computer Science},
   pages = {67-73},
   volume = {33},
   issue = {2},
   url = {http://dx.doi.org/10.1134/S036176880702003X},
   note = {10.1134/S036176880702003X},
   year = {2007}
}