Which is a certified/authentic guide to entering Jhnanas?

By far I have came across only Ajahn Brahms book which gives detailed instructions on entering Jhnanas. If I google for any other instruction manual I get this link . I don't doubt Ajahn Brahm at all but I havent read any reviews or blogs or internet postings of anyone who has entered Jhnanas through the instruction set of AB. The link seems to be talking on similar lines but different language. Is there a certified, peer reviewed instruction manual to entering Jnanas? Can you provide any other instruction manual link preferably if you have experienced it.