PDAL:

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   Generates Associated Legendre Functions of the first kind and derivatives
   
   The first index is n and the second is m
   Input is limited to -1?x?1

   Since version 1.
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   Form:
   [p, pD] = PDAL( nMax, mMax, x, xD )
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   ------
   Inputs
   ------
   nMax               Max value of first index
   mMax               Max value of second index
   x                  Argument
   xD                 Derivative of the argument

   -------
   Outputs
   -------
   p                  associated Legendre functions
   pD                 derivative of the associated Legendre functions

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   References: Spiegel, M.,R., Mathematical Handbook, McGraw-Hill
                pp 146-150 
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