O Tannenbaum O Tannenbaum "" (; "O fir tree", English: "O Christmas Tree") is a German Christmas song. Based on a traditional folk song, it became associated with the traditional Christmas tree by the early 20th century and sung as a Christmas carol. The modern lyrics were written in 1824, by the Leipzig organist, teacher and composer Ernst Anschütz. A "Tannenbaum" is a fir tree. The lyrics do not actually refer to Christmas, or describe a decorated Christmas tree. Instead, they refer to the fir's evergreen quality as a symbol of constancy and faithfulness. Anschütz based his text on a 16th-century Silesian
Allen Tannenbaum thesis advisor Heisuke Hironaka at the Harvard University in 1976. Tannenbaum has done research in numerous areas including robust control, computer vision, and biomedical imaging, having almost 500 publications. He pioneered the field of robust control with the solution of the gain margin and phase margin problems using techniques from Nevanlinna–Pick interpolation theory, which was the first H-infinity type control problem solved. Tannenbaum used techniques from elliptic curves to show that the reachability does not imply pole assignability for systems defined over polynomial rings in two or more variables over an arbitrary field. He pioneered the use of partial differential