[Tex/LaTex] LyX BibTeX with child-documents not working

Question

If I insert the bibliography within the child document, it works perfectly. (therefore it cannot be the Databank). But when I try to render the parent document, I get the following error:

 \citep
           {NatalieJ.Sayer:2007}
The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., `\hobx'), type `I' and the correct
spelling (e.g., `I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.

Answer 1

By using the natbib package you get access to different \cite commands, such as \citet and \citep.

Simply add it to your preamble by typing:

\usepackage{natbib}

For more information, please refer to the natbib package documentation