1. Hueter, Bolt, Sonics, John Wiley & Sons Ltd, p137
2. Hueter, Bolt, Sonics, John Wiley & Sons Ltd, p106
3. Olsen, Acoustical engineering, van Nostrand, p7
4. Mason, W.P., Physical acoustics and the properties of solids, van Nostrand, p43
5. Investigation of an interaction anomaly between sound projectors mounted in an array;Rusby,1962