Useful links to explanations on the correct usage of works like sino/pero, tener/haber, etc.
Just found out about this site through an online course that I'm taking. I am finding it quite useful. It helps to get another explanation regarding the 'correct' usage of these Spanish words.
BTW, there is a typo part way down the page regarding haber vs. tener - when you see the word 'heber', it's a typo for 'haber'.