https://www.chegg.com/homework-help/questions-and-answers/2-consider-grammar-s-abc-abicib-bbcid-cbbcle-ddle-show-grammar-recursive-descent-predictiv-q44707683

https://www.chegg.com/homework-help/questions-and-answers/4-say-symbol-grammar-useless-appear-derivation-strings-terminals-formally-useful-exists-de-q44707721

https://www.chegg.com/homework-help/questions-and-answers/5-consider-following-operator-grammar-ee-e-e-e-e-e-eae-e-e-e-e-id-right-associative-binary-q44707733