@article{702173,
     title = {Solutions of a linear second order equation of parabolic type defined in an unbounded domain},
     booktitle = {Differential Equations and Their Applications},
     series = {GDML\_Books},
     publisher = {Publishing House of the Czechoslovak Academy of Sciences},
     address = {Prague},
     year = {1963},
     pages = {55-63},
     mrnumber = {MR0171087},
     zbl = {0178.12602},
     url = {http://dml.mathdoc.fr/item/702173}
}

Krzyżański, M. Solutions of a linear second order equation of parabolic type defined in an unbounded domain, dans Differential Equations and Their Applications, GDML_Books,  (1963), pp. 55-63. http://gdmltest.u-ga.fr/item/702173/