\section{Acknowledgements}

Many people have helped in significant ways to get DiFX adapted for the VLBA:
Craig West for getting me interested in software correlators to begin with; 
Adam Deller for writing DiFX and helping adapt it to the needs of the VLBA; 
Steve Tingay and Matthew Bailes for allowing/encouraging Adam to write DiFX and helping support some of my travel in Australia;
Chris Phillips, John Morgan, Helge Rottmann, Mark Kettenis, Olaf Wucknitz, Mariano Muscas, Geoff Crew, John Spitzak, Roger Cappallo, Walter Max-Moerbeck and Dmitry Baksheev for contributing code, bug reports, bug fixes, and ideas;
Maria Davis, Roopesh Ojha and Dan Veillette for performing careful comparisons with geodetic data;
Walter Alef for hosting the first and second DiFX workshops in 2007 and 2008 at MPIfR, Bonn;
Miguel Guerra for helping define the database and XML structures and his work on the operator interface;
Claire Chandler and Jon Romney/ for project oversight, test planning, advice, and voices of reason;
Steven Durand for acquisition of computer and Mark5 equipment;
David Boboltz, Geoff Bower, Mark Claussen, Vivek Dhawan, Alan Fey, Vincent Fish, Ed Fomalont, David Gordon, Miller Goss, Yuri Kovalev, Matt Lister, Enno Middelberg, James Miller-Jones, Amy Mioduszewski, Leonid Petrov, Mark Reid, Lor\'{a}nt Sjouwerman and Craig Walker for working directly with or examinating the output of DiFX and providing valuable feedback;
Cormac Reynolds for maintaining the Difx wiki which hosts valuable information, hosting the third DiFX workshop in Perth, and providing lots of code;
Jan Wagner, Sergei Pogrebenko, Alexander Neidhardt, Martin Ettl, Jongsoo Kim and Randall Wayth for reporting bugs;
Eric Greisen for making AIPS work well with DiFX output;
John Benson for working with me to get data into the VLBA archive;
James Robnett, Nicole Geiger, David Halstead and Pat van Buskirk for substantial computer and networking support and useful discussions on clustering;
Mike Titus and Arthur Niell for providing test data;
Leonia Kogan for carefully reviewing the conventions used;
Pete Whiteis and Bill Sahr for contributing to helper programs;
Ken Owens and Cindy Gold at Conduant for helping resolve Mark5 issues;
Doug Gerrard, Bob McGoldrick, Adrian Rascon, K. Scott Rowe, Lothar Dahlmayer, and Jeff Long for assembling and maintaining the VLBA DiFX correlator;
Juan Cordova, Paul Dyer, Lisa Foley, Heidi Medlin, Ken Hartley, Alan Kerr, Jim Ogle, Paul Padilla, Peggy Perley, Tony Perreault, Betty Ragan, Meri Stanley and Anthony Sowinski for providing operations assistance;
Chet Ruszczyk, Dan Smythe, and John Ball for extensive Mark5 support over the last decade
and
Emma Goldberg for helping me work around the idiosyncrasies of \LaTeX \ and convince it to typeset this document.
If I left anyone of this list that should be there, and there are probably several of you in that category, I apologize --- let me know and I'll make sure to add you for the next version's document.


\begin{thebibliography}{}
\bibitem{opsplan}
	{\it VLBA-DIFX Operations Plan}, Brisken, W., 2009, VLBA Sensitivity Upgrade Memo 25, \url{http://library.nrao.edu/public/memos/vlba/up/VLBASU_25.pdf}
\bibitem{difx}
	{\it DiFX: A software correlator for very long baseline interferometry using multi-processor computing environments}, Deller, A.~T., Tingay, S.~J., Bailes, M. \& West, C., 2007, PASP 119, 318, \url{http://xxx.lanl.gov/abs/astro-ph/0702141}
\bibitem{aips102}
	{\it DiFX2: A more flexible, efficient, robust and powerful software correlator}, A.\ T.\ Deller, W.\ F.\ Brisken, C.\ J.\ Phillips, J.\ Morgan, W.\ Alef, R.\ Cappallo, E.\ Middelberg, J.\ Romney, H.\ Rottmann, S.\ J.\ Tingay, R.\ Wayth, 2011, PASP, 123, 275, \url{http://arxiv.org/abs/1101.0885}
	{\it The FITS Interferometry Data Interchange Format}, Flatters, C., AIPS Memo 102, \url{ftp://ftp.aoc.nrao.edu/pub/software/aips/TEXT/PUBL/AIPSMEMO102.PS}
\bibitem{aips114}
	{\it The FITS Interferometry Data Interchange Convention}, Greisen, E., AIPS Memo 114r, \url{ftp://ftp.aoc.nrao.edu/pub/software/aips/TEXT/PUBL/AIPSMEM114.PDF}
\bibitem{mark5-81}
	{\it Specification for enhanced Mark 5 module directory}, Whitney, A., et al., \url{http://www.haystack.mit.edu/tech/vlbi/mark5/mark5_memos/081.pdf}
\bibitem{mark5-100}
	{\it  	Mark5 User Directory Formats}, Ruszczyk, C.A., Eldering, B.\ \& Verkouter, H., \url{http://www.haystack.mit.edu/tech/vlbi/mark5/mark5_memos/100.pdf}
\bibitem{sci12}
	{\it Summary of the b-factor for the VLBA FX correlator}, Kogan, L., VLBA Scientific Memo 12, \url{http://library.nrao.edu/public/memos/vlba/sci/VLBAS_12.pdf}
\bibitem{tempo}
	{\it Tempo}, \url{http://www.atnf.csiro.au/research/pulsar/tempo/}
\bibitem{jira}
	{\it JIRA}, \url{http://bugs.aoc.nrao.edu}
\bibitem{ngas}
	{\it NGAS}, \url{http://www.eso.org/projects/dfs/dfs-shared/web/ngas/}
%\bibitem{doi}
%	{\it Difx Operator Interface Users Guide}, Guerra, M., {\bf Coming soon!}
\bibitem{vex}
	{\it VEX parameter definitions}, \url{http://www.haystack.mit.edu/tech/vlbi/mark5/vex.html}
\bibitem{wiki}
	{\it DiFX Developer Pages}, \url{http://www.atnf.csiro.au/vlbi/dokuwiki/doku.php/difx/start}
\end{thebibliography}
