20Herity, Michael. Irish Passage Graves. New York: Harper & Row, 1975. 185-86.
The author continues, "Fertility, too, is a strong and constant theme, probably represented in the inviting attitudes of the goddess of Loughcrew Cairn U and Sess Kilgreen, certainly in the phalli of Knowth and New Grange; probably also in the stones which stood erect in the chambers of Bryn Celli Ddu, New Grange and Carrowkeel Cairn F. Phallic pins and paired ball ornaments in everyday wear are constant subliminal reminders of the principle."