1. Brekhovskikh L M 1960Waves in layered media (New York: Academic Press)
2. Bullen K E 1963Theory of seismology (Cambridge University Press)
3. Churchill R V 1958Operational mathematics, New York
4. Friedlander F G 1954Commun. Pure Appl. Math. 7 705
5. Friedlander F G 1958Sound pulses (Cambridge University Press)