docs: @Reference(authors = "P. C. Mahalanobis", //
        title = "On the generalized distance in statistics", //
        booktitle = "Proceedings of the National Institute of Sciences of India. 2 (1)", //
        bibkey = "journals/misc/Mahalanobis36")
    public static double mahalanobisDistance(final double[][] B, final double[] a, final double[] c) {
      final int rowdim = B.length, coldim = getColumnDimensionality(B);
      assert rowdim == a.length : ERR_MATRIX_INNERDIM;
      assert coldim == c.length : ERR_MATRIX_INNERDIM;
      assert a.length == c.length : ERR_VEC_DIMENSIONS;
      double sum = 0.0;
      for(int k = 0; k < rowdim; k++) {
        final double[] B_k = B[k];
        double s = 0;
        for(int j = 0; j < coldim; j++) {
          s += (a[j] - c[j]) * B_k[j];
        }
        sum += (a[k] - c[k]) * s;
      }
      return sum;
    }