Trouble with combine class

What I want to do is combine several articles to form single journal volume. After some googling I found a class named combine seemingly suitable for the task. Unfortunately I had a trouble compiling very minimal code below

documentclass{combine}

begin{document}
    Some text
end{document}

The error message I get is ‘Extra endgroup. begin{document}’. I don’t know what’s going on here. How can I solve this problem? Or, is there a better alternative for combine?