Page "Bessel function" Paragraph 32

The Bessel functions of the second kind, denoted by Y < sub > α </ sub >( x ), occasionally denoted instead by N < sub > α </ sub >( x ), are solutions of the Bessel differential equation.

They have a singularity at the origin ( x = 0 ).

These are sometimes called Weber functions after Heinrich Martin Weber, and also Neumann functions after Carl Neumann.