This is the number assigned on your article from the publisher, and it's the just one you will use to reference your report throughout the library catalogues. ISSN code (also called as "ISSN structure" or "ISSN syntax") could be expressed as follows: NNNN-NNNC Indium-no cost MgSnO3 transparent conductive oxide layer: https://www.directivepublications.org/journal-of-applied-nanoscience/