1. ABFDE http://www.abfde.org/htdocs/AboutABFDE/BackgroundFunctionsPurposes.pdf
2. A statistical study of handwritings by twins and other persons of multiple births;Beacom;Journal of Forensic Sciences,1960
3. Blankers , V. van den Heuvel , E. Franke , K. Vuurpijl , L. 2009 Proceedings of the 10th International Conference on Document Analysis and Recognition
4. An investigation into the degree of similarity in the handwriting of identical and fraternal twins in New Zealand;Boot;Journal of the American Society of Questioned Document Examiners,1998