Pigeon Post Danish 1960
Publisher Thorkild Becks Forlag, CopenhagenTranslation by Kai Sørensen, cover illustrations by Axel Mathiesen
The original stories were unusually divided in two parts, each slim volume having no illustrations apart from those on the cover. The two titles mean "The Swallows and the Mysterious Man" and "The Swallows who Dig for Gold".