1. Trenagin, B. A., Asymptotic solutions of the parabolic equations with parabolic boundary layers,YMH,16, 1 (97) (1961), 163–170 (in Russian)
2. Zlama, M., The parabolic equation as a limiting case of a certain elliptic equation,Ann. Math. Pure. Appl.,57 (1962), 141–150.
3. proceeding of the praque emference;M. Zlama,1963
4. Holland, C.L., Singular perturbations in the first boundary value problems for parabolic equations,SIAM J. Math. Anal.,8, 2 (1977), 368–374.
5. Besjes, J. G., Singular perturbation problems for linear parabolic differential operators,J. Math. Anal.,48, 2 (1977), 594–609.