2015
P. Castro, M. Huber. 2015. Marine Biology. Editor for Greek Edition: Ε. Voultsiadou. Utopia Publishing. ISBN 978-618-80647-9-9. S. Gkelis translated Chapters 5 (The Microbial World) and 6 (Multicellular Primary Producers: Seaweeds and Plants).
Aquaculture. 2015. S. Gkelis authored Chapter 6 (Algae Culture). Hellenic Academic Electronic Books (Kallipos- 9932).