1. Chapter 3: ink chemistry;Brunelle,2003
2. An introduction to gel inks: history and analysis;Florence;J. Forensic Doc. Exam.,2005
3. An introduction to the gel pen;Gernandt;J. Forensic Sci.,1996
4. A study to investigate the evidential value of blue gel pen inks;Mazella;J. Forensic Sci.,2003