  This review article is a commemoration of the 30th anniversary of the
discovery of YBa2Cu3O7-delta high-temperature superconductors (HTSCs). As a
result of this discovery a family of (RE)Ba2Cu3O7-delta (RE stands for "rare
earth") HTSCs has found great practical use. The review article consists of a
brief history of how YBa2Cu3O7-delta was conceived and five sections describing
the family of compounds: crystallography, phase diagrams, manufacturing
techniques, main superconducting properties, and fields of application.
