[hpcjoe]

I'd also like to note that the Hessian matrix elements should have a \partial{\partial{l}} in each numerator, not a single \partial{l} [1].

If you aren't using LaTeX for formatting, then think partial^2 of l. FWIW: I just found this[2] which would make (using the physics package) even simpler to represent.

[1] https://en.wikipedia.org/wiki/Hessian_matrix

[2] https://tex.stackexchange.com/questions/225523/how-to-write-...