Went back to the original on the Lorenzo Thomas. "Alea's Children: the Avant-Garde on the Lower East Side, 1960-1970." in African American Review, 27:4, 1993, 573-578...

"The most remarkable thing about the Lower East Side scene was that, while race remained a powerful engine of social upheaval, the artists seemed able to work together almost in spite of it." p. 575

And...

"The relative lack of racial animosity--at least among the artists--was a notable feature of life on the Lower East Side. The fact that this atmosphere changed in the middle of the decade has, perhaps, more to do with the realities of the nation at the time than with any failure of heart among the practitioners of the avant-garde." p. 578

Also, this article from a whole section on Umbra.

Calvin Hernton in "Umbra: A Personal Recounting": "I love everything about Umbra. I love the outlandish parties we gave to raise funds to publish Umbra magazine and to keep ourselves going." p. 579