1. Air Products Ltd., Special Products Dept., Crewe, Cheshire, U.K.
2. British Oxygen Co. Ltd., Special Gas Division, Morden, London, U.K.
3. Rank Precision Industries, Margate, Kent, U.K.
4. EDT Supplies Ltd., London, U.K.
5. Calibration methods for Draeger tubes;Leichnitz;Draeger Review,1978