
 Fundamental Solutions in Elastodynamics  Cambridge University Press (Site not responding. Last check: ) 
  Component of vectors, such as displacements and forces, are always defined positive in the positive coordinate directions, and plots of displacements are always shown upright (i.e., never reversed or upside down). 
  Also, this convention calls for the use of second (cylindrical or spherical) Hankel functions when formulating wave propagation problems in infinite media, either in cylindrical or in spherical coordinates, and casting them in the frequency domain. 
  On the one hand, this convention facilitates the conversion between Cartesian and either cylindrical or spherical coordinates; on the other, it provides a convenient x–y reference system when working in horizontal planes (i.e., in a bird’seye view). 
 www.cambridge.org /catalogue/catalogue.asp?isbn=0521855705&ss=exc (875 words) 
