Rorate Coeli

When at seminary, we sang this lovely piece based on the antiphon for this Sunday's Introit. Does anyone have a clue who wrote it? Where one can purchase it? I've looked in vain for years:

"Drop down, Dew, O gracious heaven!
Let the sky rain down the Just!
Let the earth bud forth the Savior;
In Thy promise, Lord, we trust"
Thus the patriarchs were crying
While the world in bondage sighing
Sought in vain for heaven's gate
Closed by sin and Satan's hate.

God the Father in His mercy
Planned to save our fallen race,
Whilst the burden of our sinning
God the Son deigned to embrace;
God the Spirit gave His token
Through the Virgin who had spoken:
"Lo, Thy handmaid, Lord hath heard;
Work in me Thy wondrous Word!"

Then the Son took man's frail nature,
Was made flesh and dwelt on earth.
Life and light with grace abundant
He bestows of priceless worth.
Earth, rejoice! Exult with gladness!
A new Sun dispels all sadness!
Let us then our voices raise,
Let us sing our Savior's praise.