A specific factors model with a single specific factor in each industry and one mobile factor, named after two of the many who used this as the standard model of trade prior to the Heckscher-Ohlin Model. It extends the simple Ricardian Model by allowing the marginal product of labor to fall with output. It was revived by Jones (1971), Samuelson (1971), then merged with H-O by Mayer (1974), Mussa (1974), and Neary (1978).