Edit - maybe I have the notaton figured out now and am just confused. 1. The problem statement, all variables and given/known data The below relevant quotations come from Landau and Lifgarbagez, volume 7 : The theory of elasticity, chapter 1. 2. Relevant quotations Page 2: where uik is the strain tensor, dl is the original distance between two points, and dl' is the deformed distance between the two points. xi are co-ordinates. ^^^Where, in the book, D is a squigly d (lower case delta?). Looks like the d used in variations. Page 5 (last paragraph): 3. The attempt at a solution In quotation 2 - where did D come from? What is it? In quotation 3 - Is he using Einstiein summation notation still, because I don't understand why there would only be two components of the force, or two co-ordinates, because everything so far as been 3 dimensional. I don't understand how this is the moment tensor (it does make sense if its done for all 3 2d planes (xy, yz, zx), and Fi is a component of force in the i direction, then it's a scalar returned for the norm of the moment, directed in the direction normal to the plane - but then you get either a 2nd order diagonal tensor, or a first order tensor, neither of which is an antisymmetrical tensor of rank 2) Thanks for your help.