1. DIN EN 571-1:1997. Non-destructive testing - Penetrant testing - Part 1: General principles; German version EN 571-1:1997. 10 p.

2. ASTM E 1417 / E 1417M. Standard Practice for Liquid Penetrant Testing. ASTM Int., 2013. 11 p.

3. CFPM-MASTER. Fluorescent Penetrant Method - Master. Pratt & Whitney Canada, 2001. 18 p.

4. QPL AMS 2644. Qualified Product List of Products Qualified under Performance Specification SAE-AMS2644. Inspection Material, Penetrant. 2012. - 21 p.

5. DIN EN 4179 / NAS 410-2011. Aerospace series - Qualification and approval of personnel for non-destructive testing. 2011. 52 p.