https://scottbarrykaufman.com/who-created-maslows-iconic-pyramid/

And his credentials:

Scott Barry Kaufman is among the top 1% most cited scientists in the world … Dr. Kaufman hosts the The Psychology Podcast  which has received over 30 million downloads and is frequently ranked the #1 psychology podcast in the world.

When psychologist Scott Barry Kaufman first discovered Maslow’s unfinished theory of transcendence, sprinkled throughout a cache of unpublished journals, lectures, and essays, he felt a deep resonance with his own work and life. In this groundbreaking book, Kaufman picks up where Maslow left off, unraveling the mysteries of his unfinished theory, and integrating these ideas with the latest research on attachment, connection, creativity, love, purpose and other building blocks of a life well lived.