Oracle Database 12c DBA Handbook by Bob Bryla: Used

Oracle Database 12c New Features

Oracle SQL Tuning with Oracle SQLTXPLAIN: Oracle Database 12c Edition

Oracle Database 12c SQL Master SQL and PL/SQL Paperback Book

Oracle SQL Tuning with Oracle SQLTXPLAIN: Oracle Database 12c Edi

Oracle PL/SQL Programming : Covers Versions Through Oracle Database 12c(518)

Oracle Essentials: Oracle Database 12c, Greenwald, Rick,Stern, Jonathan,Stackowi

Beginning Oracle SQL: For Oracle Database 12c