@Misc{ 
  butkog10,
  author = { Buttazzo, Giuseppe and Kogut, Peter },
  title = { Weak Optimal Controls in Coefficients for Linear Elliptic Problems },
  journal = {  },
  year = { 2010 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/487/ },
  note = { cvgmt preprint}
}