[The material on Trees under Howson is probably more current than this. If you'd like me to update these Tree Notes, send me an email mfricke@SoftOption.Us .]
This section of the tutorials and
M.Bergmann, J.Moor, J.Nelson [2008], The Logic Book [the current edition is the 5th edition]
would work well together.
You need to know some propositional logic to be able to understand the tutorials to come. In particular, you need to know about the symbols used in propositional logic, truth tables, satisfiability, consistency, and semantic invalidity (by counter example). You do not need to know propositional rules of inference and derivations.
Bergmann [2008] will give you enough background.
Alternatively you could look at the first four propositional tutorials in Easy Deriver: Bergmann
You should perhaps also check Checking your computer is configured correctly and Writing Symbols (and Alternative Symbols)
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