1. R.W. Carroll, R.E. Showalter, Singular and Degenerate Cauchy Problems (Academic, New York, 1976)
2. R.W. Carroll, Transmutation and Operator Differential Equations (North Holland, Amsterdam, 1979)
3. R.W. Carroll, Transmutation, Scattering Theory and Special Functions (North Holland, Amsterdam, 1982)
4. R.W. Carroll, Transmutation Theory and Applications (North Holland, Amsterdam, 1986)
5. V.V. Katrakhov, S.M. Sitnik, The transmutation method and boundary–value problems for singular elliptic equations. Contemp. Math. Fund. Dir. 4(2), 211–426 (2018, in Russian)