The surplus procedure (SP) is a fair division protocol for dividing goods in a way that achieves proportional equitability. It can be generalized to more than 2=two people and is strategyproof. For three or more people it is not always possible to achieve a division that is both equitable and envy-free.
The surplus procedure was devised by Steven J. Brams, Michael A. Jones, and Christian Klamler in 2006.
Surplus procedure Wikipedia
There have been a few criticisms of aspects of the paper. In effect the paper should cite a weaker form of Pareto optimality and suppose the measures are always strictly positive.