Parvin Asadzadeh Rajkumar Buyya Chun Ling Kei Deepa Nayar Srikumar Venugopal Global Grids and Software Toolkits: A Study of Four Grid Middleware Technologies http://arxiv.org/abs/cs.DC/0407001 2004 CoRR cs.DC/0407001 db/journals/corr/corr0407.html#cs-DC-0407001 informal publication