For a coequality q we say that it is regular coequality on set X ordered under the antiorder ̨ if there exists an anti-order on X=q such that the natural mapping W X ! X=q is a reverse isotone surjection of anti-ordered sets. The lattice of regular coequalities is described. 2000 Mathematics Subject Classification: 03F65, 06F05

The continuous-time version of Kyle’s (1985) model of asset pricing with asymmetric information is studied, and generalized in various directions, i.e., by allowing time-varying liquidity trading, and by having weaker a priori assumptions on the model. This extension is made possible by the use of filtering theory. We derive the optimal trade for an insider and the corresponding price of the ri...