Who said "Gratitude must be earned through genuine service."?

This quote is attributed to Lewis Strauss.

Gratitude must be earned through genuine service. - Lewis Strauss

"Gratitude must be earned through genuine service."

Lewis Strauss Gratitude

"I have a memory, and I intend to use it."

"The world is not kind to those who hesitate."

"Power is not given; it is taken."

"History will judge us all eventually."

"Gratitude makes life richer."

"A grateful heart is a happy heart."

"Respect those who came before us."

"Life's greatest treasures are the people we love"