Authors:

It's [motherhood] the biggest on-the-job- training program in existence today.

Erma Bombeck (2013). “The Erma Bombeck Collection: If Life Is a Bowl of Cherries, What Am I Doing in the Pits?, Motherhood, and The Grass Is Always Greener Over the Septic Tank”, p.165, Open Road Media
It's [motherhood] the biggest on-the-job- training program in existence today.