I am so sorry for your loss. Mr. Phelps was blessed with 89 years of special mightiness. (Psalms 90:10) May your hearts be filled with joyful memories of time spent with him. May the Hearer of Prayer bring you strength and peace in your time of sorrow.
I referenced Dr Phelp's work in the first scientific paper I wrote. Though I never met him, I have known many who did and who speak of him with the highest regard. I pass on my respect for Dr phelps and my condelences to his family and friends.
To the Phelps family, offering my deepest sympathies during this difficult time. May you find comfort in these words..."he will wipe out every tear from their eyes and death will be no more, neither will mourning nor outcry nor pain be anymore. The former things have passed away."