@misc{Laulajainen_Risto_When_2013, author={Laulajainen, Risto}, volume={86}, number={2}, copyright={Rights Reserved - Free Access}, address={Warszawa}, journal={Geographia Polonica}, howpublished={online}, year={2013}, publisher={IGiPZ PAN}, language={eng}, type={Text}, title={When to stop collecting data on ship movements?}, URL={http://rcin.org.pl/igipz/Content/33937/PDF/WA51_51244_r2013-t86-no2_G-Polonica-Laulajain.pdf}, keywords={cargo value, port visit, regional differentiation, size class, value gap, ship movement}, }