@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://www.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},
}