\BOOKMARK [1][-]{section.1}{Introduction and main results}{}% 1
\BOOKMARK [1][-]{section.2}{Examples}{}% 2
\BOOKMARK [1][-]{section.3}{Proofs}{}% 3
\BOOKMARK [1][-]{section.4}{Future research}{}% 4
\BOOKMARK [1][-]{section.5}{Acknowledgments}{}% 5