Title: Hoch-T[subscript c]-Supraleitung in den Systemen YBa₂Cu[subscript 3-x]A[subscript x]O[subscript 7±z] (A = Co, Li) und Bi₁.₅Pb₀.₅Sr₂Ca[subscript 1-x]Gd[subscript x]Cu₂O[subscript 8+z]