Uoorthvajaanu is a karana among the 108 karanas of bharatanatya. It should have been pretty famous among the artisans of chola empire - for it finds depiction in many temples of that era.
Wen we went to meet Dr.Kalaikkovan and Dr.Nalani for the second time, they distributed a research paper titled "Rare karana sculptures from thirumazhapadi" - with Dr.K's autograph.
The article lays its focus mainly on this karana, its variations in thirumazhapadi sculptures etc. In this article, they also quote references from bharatha natya sastra - the actual karana, how it is depicted in other temples, why mazhapadi karanas are unique etc.
I've uploaded one of the pictures from the cover page of Varalaaru Issue 1 in PS files section. I'll try to upload the article as well.