The Fortran 90 TriStream routine is an adaptation of the Matlab script of
same name. The original Matlab script file is available at:
       https://fr.mathworks.com/matlabcentral/fileexchange/11278-tristream
It is written by Matthew Wolinsky.

As mentioned in the header of the Matlab script file, the algorithm follows
the approach outlined in the paper:
        "Efficient Streamline Computations on Unstructured Grids" by
        Mihai Dorobantu       http://citeseer.ist.psu.edu/40044.html

Modifications have been made (see the file CHANGES), mainly to fix numerous
pathological cases. Also, another important change is to discard null root
of R(1:3), to avoid zero value of stepsize dt. Indeed, it is not unusual to
find simple examples of triangles which lead to zero value of one component
of R.

License is not known.
