como adicionar artigo de citação no Springer?

Question

Quero adicionar algumas citações no artigo do jornal Springer da seguinte maneira, mas isso nunca funciona. nomeadamente:? ?

Arquivo texto

\RequirePackage{fix-cm}
%

%\documentclass{svjour3}                     % onecolumn (standard format)
%\documentclass[smallcondensed]{svjour3}     % onecolumn (ditto)
\documentclass[smallextended]{svjour3}       % onecolumn (second format)
%\documentclass[twocolumn]{svjour3}          % twocolumn
%
\smartqed  % flush right qed marks, e.g. at end of proof
%
\usepackage{graphicx}
\usepackage{natbib}


\begin{document}

\citep{Hvala}, \citep{Birkenmeier}

\bibliographystyle{spbasic}
\bibliography{litera}   % name your BibTeX data base



\end{document}
% end of file template.tex

Arquivo de babador

@article{Hvala,
    author = {Hvala, B.},
    title = {Generalized derivations in rings},
    journal = {Comm. Algebra},
    volume = 26,
    pages = {1147--1166},
    year = 1998,
}
@inproceedings{Birkenmeier,
    author = {Birkenmeier, G. F. and Heatherly, H. E. and Lee, E. K.},
    title = {Completely prime ideals and radicals in Near-rings},
    booktitle = {Proceedings of Near-rings and Near-Fields},
    publisher = {Kluwer},
    year = 1995,
    pages = {63--73},
    editor = {Fong, Y. and others},
}

Muito obrigado antecipadamente!