@Techreport{elahmad2011robustness,
  author = {El Ahmad, Ahmad S and Yan, Jeff and Tayara, Mohamad},
  title  = {The Robustness of Google CAPTCHAs},

  year   = {2011},
  number = {},
  url    = {http://homepages.cs.ncl.ac.uk/jeff.yan/google.pdf},

  const  = {\ text}
}
@Article{melnik2010dremel,
  author = {Melnik, Sergey and Gubarev, Andrey and Long, Jing Jing and Romer, Geoffrey and Shivakumar, Shiva and Tolton, Matt and Vassilakis, Theo},
  title  = {Dremel: interactive analysis of web-scale datasets},
  journal = {Proceedings of the VLDB Endowment},
  year   = {2010},
  number = {1-2},
  url    = {http://dl.acm.org/citation.cfm?id=1920841.1920886},

  const  = {\ text}
}