Stacking up state transformers

Thanks to Andrew, I'm now backtracking my state correctly. Now what I want to do is have two elements of state, an element that gets backtracked, and an element that doesn't. My monad now looks like this: type NondetState bs ns a = StateT bs (NondetT (StateT ns Maybe)) a where bs is my backtracked state, and ns my non-backtracked state. I can still access my backtracked state using Control.Monad.State.{get,put}, but I can't access my non-backtracked state. How do I burrow through the stack of monad transformers to get and put the 'ns' state? Supplementary question: What documentation should I be reading? cheers, Simon