Bessel function

When I see equations, I see the letters in colors – I don’t know why. As I’m talking, I see vague pictures of Bessel functions from Jahnke and Ernde’s book, with light-tan j’s, slightly violet-bluish n’s, and dark brown x’s flying around. And I wonder what the hell it must look like to the students.

— Bessel function

[To use spherical harmonies or Bessel functions is] to be able to start in mathematics in Cambridge just about the place where some of the best mathematical men now end their studies forever.

— Bessel function