Talk:Formal Logic/Sentential Logic/Properties of Sentential Connectives

more explanation and examples would be useful
Is this book a reference book or is it for pedagogy? I'm learning logic from it. The symbol that looks like |= is not explained. Why do we have |= |= =| and -> at different times? It's not clear what they mean. There should be sporadic examples, such as Conditional Addition: 1. -P therefore 2. P->Q	    conditional addition (1) We need to teach what you can do with these laws.