4th December 1973: Opera singers Maria Callas (1923 - 1977) and Giuseppe Di Stefano at a farewell concert at the Festival Hall, London. (Photo by Tim Graham/Evening Standard/Getty Images)
4th December 1973: Opera singers Maria Callas (1923 - 1977) and Giuseppe Di Stefano at a farewell concert at the Festival Hall, London. (Photo by Tim Graham/Evening Standard/Getty Images)