1. Chapter 6 of “Experimental Methods for Engineers”, 6th edition (Pressure Measurement): By J.P. Holman, 1994.
2. Electronic Pressure Measurement Basics, applications and instrument selection: By M/s Eugen Gaßmann, Anna Gries (technical collaboration of M/s WIKA Alexander Wiegand SE & Co. KG.). First published in Germany in the series Die Bibliothek der Technik Original title: Elektronische Druckmesstechnik © 2009 by Süddeutscher Verlag onpact GmbH.
3. Product Bulletin for Sight Glass Level Gauges of M/s PHONIX MESSTECHNIK GmbH.
4. Pubblicazione B09 – 01 – Rev.00. Eng : By M/s CESARE BONETTI S.p.A. Product Catalog.
5. Machinery’s Handbook, 29th Edition. Erik Oberg, Franklin Jones, Holbrook Horton, Henry Ryffel, Christopher McCauley 2800 Pages, Hardcover Published: January, 2012 ISBN: 9780831129002.