Get the Whitepaper called Optimizacion de SQL Union Injection en MYSQL. Written in Spanish.
You can download it from the following link: https://packetstormsecurity.com/files/download/80054/sql-optimization.pdf
Source: https://packetstormsecurity.com/files/80054/Whitepaper-Optimizaci-n-de-SQL-Union-Injection-en-MYSQL.html