yes, you need to import other opengl classes too, since methods are in the classes depending on the OpenGL version they were introduced. Usually the best way to do this is by using the OpenGL SDK http://www.opengl.org/sdk/
e.g. If I want to use glShaderSource, the docs (notes section)
here tell you that it was introduced in OpenGL 2.0, hence you would need to import GL20.