@incollection{Ahmed_2006,
    doi = {10.1007/11693024_6},
    url = {https://doi.org/10.1007%2F11693024_6},
    year = {2006},
    publisher = {Springer Berlin Heidelberg},
    pages = {69--83},
    author = {Amal Ahmed},
    title = {Step-Indexed Syntactic Logical Relations for Recursive and Quantified Types},
    booktitle = {Programming Languages and Systems}
}

@incollection{Ahmed_2006, doi = {10.1007/11693024_6}, url = {https://doi.org/10.1007%2F11693024_6}, year = {2006}, publisher = {Springer Berlin Heidelberg}, pages = {69--83}, author = {Amal Ahmed}, title = {Step-Indexed Syntactic Logical Relations for Recursive and Quantified Types}, booktitle = {Programming Languages and Systems} }