1. T. Nishimoto, ?A turning point problem of an n-th-order differential equation of hydrodynamic type,? Kodai Math. Sem. Repts.,20, 218?256 (1968).
2. P. E. Tovstik, ?Integrals of a linear equation of order m+n with a small parameter for the derivatives,? Diff. Uravn.,6, No. 6, 989?999 (1970).
3. M. A. Kovalevskii, ?The constructions of fundamental families of solutions and the problem of their connections for a linear differential equation of hydrodynamic type with a turning point and a regular singularity,? Diff. Uravn.,18, No. 6, 948?956 (1982).
4. K. Okubo, ?A global representation of a fundamental set of solutions and a Stokes phenomenon for a system of linear ordinary differential equations,? J. Math. Soc. Jpn.,15, No. 3, 268?288 (1963).
5. H.-G. Roos, ?Die Konstruction eines asymptotischen Fundamentalsystems für eine linear Differentialgleichung vom hydrodynamischen Typ,? Z. Angew. Math. Mech.,55, No. 9, 401?407 (1976).