My 86 Year Old Father (very Active Still And Ex

My 86 year old father (very active still and ex surgeon) is taking oxycodone that was prescribed to his wife for paid after hip surgery because he says it helps him sleep. He says he takes a half tab of her low dose oxy. From what I've read this is extremely dangerous on two levels...addiction and overdose potential in taking a broken pill. I am looking for an article to send him to read but only seem to be able to find blog strings on the dangers of what he is doing. Could you suggest a website that I can go to that will address the dangers of what he is doing.