### PDH’s PDF Utils

I wrote a program for Mac OS X (10.5+) that manipulates graphics files. Mostly I use it to convert an .eps to a small .pdf, but the program does some other things. The program comes with no warranty whatsoever. Download PDH’s PDF Utils.

### SAGE notebooks

Sage is a computer algebra system that is open-source. I had to zip the Sage worksheet files (sws) in order to upload them to my server, and I recommend using StuffIt Expander to unzip them. There should be a .sws file when unzipped properly.

- d-invariants.sws.zip: computes the d-invariants of lens spaces
- delta-one-via-grobner-basis.sws.zip: computes \(\delta_1\) of any knot in \(S^3\). See the readme