[Tex/LaTex] Unwanted white space in references

bibtex

I am getting unwanted whitespace in references.

unwanted out put

I am using these packages for my bibliography 

\usepackage[round, sort, numbers]{natbib}
\usepackage[numbib]{tocbibind}
\renewcommand{\bibname}{References}

These are my lines to create the bibliography

\bibliographystyle{plainnat}
\bibliography{references}

And my .bib entries are as follows

@booklet{NaveDP,
author = {Nave},
title = {Law of Dulong and Petit},
year = {2014},
howpublished = {url},
}

@booklet{NaveDB,
author = {Nave},
title = {Debye's Contribution to Specific Heat Theory},
year = {2014},
howpublished = {url},
}

@booklet{Brown,
author = {Robert G. Brown},
title = {First Law of Thermodynamics Summary},
year = {2004},
howpublished = {url},
}

Best Answer

You need little help from the package url as mentioned by bombcar.

\documentclass{article}
\usepackage{filecontents}
\begin{filecontents*}{mybib.bib}
  @booklet{NaveDP,
author = {Nave},
title = {{Law of Dulong and Petit}},        %% note extra pair of braces
year = {2014},
howpublished = {\url{http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/dulong.html}},
}

@booklet{NaveDB,
author = {Nave},
title = {Debye's Contribution to Specific Heat Theory},
year = {2014},
howpublished = {\url{http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/debye.html}},
}

@booklet{Brown,
author = {Robert G. Brown},
title = {First Law of Thermodynamics Summary},
year = {2004},
howpublished = {\url{http://phy.duke.edu/rgb/Class/phy51/phy51/node59.html}},
}
\end{filecontents*}
\usepackage[round, sort, numbers]{natbib}
\usepackage[numbib]{tocbibind}
\renewcommand{\bibname}{References}
\usepackage{url}
\begin{document}
  \nocite{*}
  \bibliographystyle{plainnat}
  \bibliography{mybib}
\end{document}

enter image description here

What I did:

I wrote the howpublished data field as 

howpublished = {\url{http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/dulong.html}},

using \url command after loading url package. This should be done for all urls.

To prevent bibtex from converting Dulong and Petit in to lower case, an extra pair of braces is used (thanks to Mico for picking it up).

{{Law of Dulong and Petit}}
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