UP and the Low and High Hierarchies: A Relativized Separation. - Ming-Jye Sheu; Timothy J. Long (ICALP, 1992)

The Extended Low Hierarchy is an Infinite Hierarchy. - Ming-Jye Sheu; Timothy J. Long (SIAM J. Comput., 1994)

A Refinement of the Low and High Hierarchies. - Timothy J. Long; Ming-Jye Sheu (Math. Syst. Theory, 1995)

UP and the Low and High Hierarchies: A Relativized Separatin. - Ming-Jye Sheu; Timothy J. Long (Math. Syst. Theory, 1996)