Who is the Author of this poem? And Where was it Presented?

[laplaza]

We run because we must
Through the great wide spaces.
Within each man exists a demon
Some men quiet it,
Other men are driven by it.
In being driven
They encounter loneliness
But. they discover themselves.
And find exhilaration,
They find too, a peace
Which many men seek,
But few attain,
I congratulate the long distance
Runner for his self-discipline.
I share with him his loneliness,
I envy him his peace.