On canonical mappings onto circular domains with radial slits

New definitions of normal (in the sense of GrЁotzsch) annular and circular domains with radial slits are considered. Their geometric and functional properties are established. Arguments based on the method of extremal metric in the sense of Fuglede allow one to extend these properties to the $n$-dimensional case, $n\geqslant2$. The properties established provide a means for simplifying the proofs of the related results by Strebel and Reich and for bringing them to a complete form. Bibliography: 12 titles.