References
==========

Quadrilateral HPS
-----------------

The quadrilateral HPS implementation is a reduced Python version of the MATLAB
Surfacefun package:

https://github.com/danfortunato/surfacefun

Fortunato, D. (2024). *A high-order fast direct solver for surface PDEs*.
SIAM Journal on Scientific Computing, 46(4), A2582-A2606.

Triangular HPS
--------------

The triangular formulation and fast direct solver framework are introduced in:

*A High-Order Fast Direct Solver for Surface PDEs on Triangles*

https://arxiv.org/pdf/2604.03097