Pushdown Accepters & Context-Free Grammars. Sipser, Theorem 2.12 Denning, Chapter 8. Fundamental theorem of CFLs and PDAs. Theorem 2.12 (Sipser) A language L is context-free if and only if (iff) there exists a pushdown accepter M that recognizes L. CFL if PDA; PDA -> CFL.
Sipser, Theorem 2.12
Denning, Chapter 8