\BOOKMARK [1][-]{section.1}{Introduction}{}% 1
\BOOKMARK [1][-]{section.2}{Finite subsets of A}{}% 2
\BOOKMARK [1][-]{section.3}{Infinite subsets of N and A}{}% 3
\BOOKMARK [1][-]{section.4}{Asymptotic results}{}% 4
\BOOKMARK [1][-]{section.5}{Acknowledgements}{}% 5