The routines described in this section compute the Cylindrical Bessel functions @math{J_n(x)}, @math{Y_n(x)}, Modified cylindrical Bessel functions @math{I_n(x)}, @math{K_n(x)}, Spherical Bessel functions @math{j_l(x)}, @math{y_l(x)}, and Modified Spherical Bessel functions @math{i_l(x)}, @math{k_l(x)}. For more information see Abramowitz & Stegun, Chapters 9 and 10. The Bessel functions are defined in the header file `gsl_sf_bessel.h'.