Lineage & Ancestry of HRH Prince Charles, Prince of Wales @ Vol I p 56, d of Bjorn Bearsson & sister of Siward E of Northumberland
The cited information was published by Skilton, Edinburgh, Scotland, 1977 (Ref: Vol I p 56, d of Bjorn Bearsson & sister of Siward E of Northumberland) The author/originator was Gerald Paget.