1. An ultrasonic flowmeter for the accurate measurement of high pressure gas flows;Nolan,1983
2. Ultrasonic flowmeters for the gas industry;Nolan,1988
3. British Patent No. 1503 852, filed April 1975. Published March 1978, Westinghouse Electric Corporation
4. Development in the ultrasonic flowmeter in British Gas;Nolan,1984
5. British Gas test facility at Bishop Auckland;Norman,1986