Stephen's final paper, A smooth exit from eternal inflation?, was co-authored with Thomas Hertog.
The general basis of this paper has to do with the physics that are involved in positioning multiple
universes.  They ended up concluding that in their new model, all universes must share some law or
laws of physics.  I am including the paper here in case you are interested in reading it.  This paper was
submitted to the Journal of High Energy Physics 10 days before Stephen Hawking passed away and can
be downloaded at no cost and you can access it here.