We wish to thank current active contributors to PSPP: * Ben Pfaff wrote the initial program and manual, which comprises the majority of the current code. Ben continues to contribute and most of the core libraries which ensure that PSPP runs with optimal speed are his work. * John Darrington wrote the graphical user interface, and the T-TEST, ONEWAY, EXAMINE, RANK and NPAR TESTS commands, implemented support for long variable names, PostgreSQL and Gnumeric and made numerous revisions to other modules. * Jason Stover contributed statistical and numerical functionality, including lib/gslextras and the linear regression features. Jason is also an important contributor to GSL, which is used by PSPP. We also thank past contributors: * John Williams wrote an initial draft of the T-TEST procedure. * Michael Kiefte contributed bug fixes and other enhancements. * Patrick Kobly contributed bug fixes and other enhancements. * Rob van Son wrote the original version of the routine for calculation of the significance of the Wilcoxon matched pairs signed rank statistic used by the NPAR TEST command.