The last issue of 2019 (Vol. 30, No. 4) as general issue is available online (http://www.aps-polar.org/paper/2019/30/04/). Its print publication is to be complete soon.
In this issue, two Editorial Opinions, one Review, four Articles and one Trend were published. The authors come from seven different countries (Belgium, Canada, China, France, New Zealand, Portugal, USA).
We appreciate the editors, guest editors, authors and reviewers for their great efforts in completing Volume 30.