[yt-users] Notebook server question

Hello yt users, I have a (perhaps naive) ssh question related to the yt notebook. I would like to run a yt notebook server on machine A. However, machine A cannot be directly accessed via ssh from the wider internet. Instead, I must first ssh into machine B, and then ssh from B to A. Machine B cannot run the notebook server itself. Does anyone know how I can configure things - perhaps by using a more complicated ssh tunnel command - so I that access a notebook server running on machine A through machine B? Thanks, Andrew