Prefacio
(1960)
Foreword
(1960)
Elösó
(1960)
Préface
(1960)
Önsöz
(1960)
Foreword
(1960)
Przdemova
(1960)
Introdução
(1960)
(Foreword, Swedish)
(1960)
(Foreword, Greek)
(1960)