A solution with biblatex
and the program biber
\RequirePackage{filecontents}
\begin{filecontents*}{\jobname.bib}
@article{Pablo2016,
author={H. Pablo and G. N. Whittaker and A. Popowicz and S. M. Mochnacki and R. Kuschnig
and C.
C. Grant and A. F. J. Moffat and S. M.
Rucinski and J. M. Matthews and A. Schwarzenberg-Czerny and G. Handler and W. W. Weiss
and
D. Baade and G. A. Wade and E.
Zocłońska and T. Ramiaramanantsoa and M. Unterberger and K. Zwintz and A. Pigulski and
J.
Rowe and O. Koudelka and P.
Orleański and A. Pamyatnykh and C. Neiner and R. Wawrzaszek and G. Marciniszyn and P.
Romano and G. Woźniak and T.},
title ={An article with a lot of authors},
date ={2018-12-20},
journal= {The journal for Articles},
location ={New York and Bangkok},
}
\end{filecontents*}
\documentclass{article}
\usepackage[czech]{babel}
\usepackage{csquotes}
\usepackage[style=authoryear,maxbibnames=99]{biblatex}
\addbibresource{\jobname.bib}
\begin{document}
foo~\parencite{Pablo2016} or bar~\textcite{Pablo2016}
\printbibliography[title=Seznam použité literatury]
\makeatletter % only for demonstration
\def\blx@maxbibnames{1}
\blx@resetdata
\makeatother
\printbibliography[title=Seznam použité literatury]
\end{document}

Using biblatex
instead of BibTeX and bibliographysytle
. is not really difficult: Replace your
\bibliographystyle{czplainnat}
\renewcommand{\bibname}{Seznam použité literatury}
\bibliography{literatura}
with the following which should go into the preamble(!):
\usepackage[style=authoryear,maxbibnames=1]{biblatex}
\addbibresource{<your bibfile>.bib}
in the text use \textcite
, \parencite, or simply
\cite` and at the end
\printbibliography[title=Seznam použité literatury]
\dots
between the 7th and last authors. Ulrike's comment shows you how to control the numbers in the more simple cases if needed. Somebiblatex
(as your tagging suggests). If you are not usingbiblatex
a different method may be needed. Please show us not only your.bib
entry but also a short example document that demonstrates which bibliography and citation packages you load (e.g.cite
,natbib
,jurabib
,biblatex
, ...), which style you use (the argument of\bibliographystyle
for BibTeX-based solution or the value of thestyle
option forbiblatex
) and how you create your bibliography.czplainnat
has no built-in option to restrict the number of displayed names as easily asbiblatex
.