Ships and marine technology – Graphical symbols for technical documentation – Part 4: Sounding pipes, air pipes and filling pipes; Text in German and English
standard by Deutsches Institut Fur Normung E.V. (German National Standard), 10/01/2012

Ships and marine technology – Graphical symbols for technical documentation – Part 4: Sounding pipes, air-pipes and filling pipes
standard by Deutsches Institut Fur Normung E.V. (German National Standard), 11/01/1999