@Manual{vwline-pkg,
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year ={2017}
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@techreport{vwline-intro,
title="Variable-Width Lines in {R}",
    author = {Paul Murrell},
year={2017},
institution={University of Auckland},
number={2017-01},
url={http://stattech.wordpress.fos.auckland.ac.nz/2017/05/19/2017-01-variable-width-lines-in-r/}
}

@techreport{ends-and-joins,
title="Variable-Width Line Ends and Line Joins",
    author = {Paul Murrell},
year={2017},
institution={University of Auckland},
number={2017-02},
url={http://stattech.wordpress.fos.auckland.ac.nz/2017/05/19/2017-02/}
}

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@book{apostol2007calculus,
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  @Manual{Ryacas,
    title = {Ryacas: R Interface to the {Yacas} Computer Algebra System},
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@inproceedings{yacas,
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 acmid = {750655},
 publisher = {Springer-Verlag},
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}