My parents need educational material on my husband's ADHD

My husband was diagnosed with ADHD only about 6 months ago. My mom and dad are our good friends and are the people we usually go to when we need advice. However, since the diagnosis and starting treatment (medication and counseling) my dad has started showing irritation toward my husband--almost as if he has no more patience for him anymore. We’ve explained in basic terms what ADHD is and how an ADHD brain works, but my dad either does not believe it is legitimate or maybe feels inadequate in understanding what support my husband and I need so he is coming across annoyed unintentionally. I do not know. I am going to talk to him soon because it is hurting us, but I want to bring him and my mom something educational to read. Are there any articles or books written for an ADHD person’s support people??