I found that paper “Compatible Embeddings”
In Pascal Barla’s blog (Research projects, prototype software, random stuff, notes and new ideas)
You can watch that video to have a rapid overview of the N-Way morhping
Edit (few minutes later) You can download 4.6Mo pdf Publication N-way morphing for 2D Animation, William Baxter, Pascal Barla, Ken-ichi Anjyo, Computer Animation and Virtual Worlds (Proceedings of CASA), Volume 20, Number 2 – 2009
see(:ya!