Revert "Revert "y3, y4 terms not in Catena paper (though the values are very small)""
Revert "Revert "y3, y4 terms not in Catena paper (though the values are very small)""

This reverts commit 529e366e71323309dcc56653776c2571f0c27f42.

aaronvincent/captngen