There is no ordering on the classes in the generalized high/low hierarchies.

Antonio Montalbán There is no ordering on the classes in the generalized high/low hierarchies. 215-231 2006 45 Arch. Math. Log. 2 http://dx.doi.org/10.1007/s00153-005-0304-0 db/journals/aml/aml45.html#Montalban06