Looking for best article to explain Alzheimers to my dad to help him be compassionate to my mom, who has Alzheimers.

My 85 year old mother is in the middle stage of Alzheimers and lives with my 88 year old father in their home. My father does not understand Alzheimer's and gets very curt with her and sometimes yells when she repeats a questions several times. He completely loses his patience with her and has accused her of lying when she states something as the truth or blames someone else like a doctor's office by saying that they never call her back, when in fact she spoke to them that same morning. (I call it "her truth"). I have tried to explain to him that it is the Alzheimers, and she cannot process his answer(s), which is why the question is repeated and that her short term memory is lapsing. How can I explain to him what she is going through and that she is not lying. He is an educated man and I am at my wits end as to why he does not understand what she's going through and he is making matters worse by his reactions. We are working toward assisted living for both of them and currently have a nurse coming in to give my mom her medications. I live near them and visit often and talk with them every day. It would be best if someone could recommend a good article for my dad to read, as I have tried to explain it to him many times. I am looking for something that explains to the caregiver what makes the person with Alzheimers not capable of processing new information and how best to react to them. I have been to Alzheimers.org, but haven't found anything that is on point. Any input is welcomed. Thank you.