Tim Henstock contributed the segy supplement, while Kurt Feigl and Genevieve Patau wrote the seis supplement. Dennis Milbert donated the Fortran code that was translated to become earthtide.c. David Sandwell contributed the img supplement.
We would also like to acknowledge feedback, suggestions and bug reports from Andreas Bjørnestad, Michael Barck, Manfred Brands, Allen Cogbill, Stephan Eickschen, John Helly, Ben Horner-Johnson, Kristof Koch, John Kuhn, Angel Li, Andrew Macrae, Alex Madon, Ken McLean, Greg Neumann, Ameet Raval, John Robbins, Georg Schwarz, Richard Signell, Peter Schmidt, Dirk Stoecker, Eduardo Suárez, Mikhail Tchernychev, Malte Thoma, David Townsend, Garry Vaughan, William Weibel, and many others, including their advice on how to make GMT portable to a wide range of platforms. John Lillibridge and Stephan Eickschen provided the original Examples (11) and (32), respectively; Hanno von Lom helped resolve early problems with DLL libraries for Win32; Lloyd Parkes enabled indexed color images in PostScript; Brent Wood developed the GMT/OGR format; Wayne Wilson implemented the full general perspective projection; and William Yip helped translate GMT to POSIX ANSI C and incorporate netCDF 3. The SOEST RCF staff (Ross Ishida, Pat Townsend, and Sharon Stahl) provided valuable help on Linux and web server support.