I have seen few journals which are indexed in well known databases like Zentralblatt MATH, AMS Digital Mathematics, CiteFactor but still does not assign DOI numbers to published articles, what could be the reason? Is this a common thing ? Does DOI number add any value to authenticity of journal ? Most importantly which purpose does this DOI number serve ?
I am asking this because I have heard if journal do not assign DOI number to its published articles then it could be low profile journal or even could be fake. The similar question has been asked in Why do some papers not have a DOI?, but my query related to quality/authenticity of journal could not be resolved.
PS. My question is related to authenticity of journal "Computational Methods for Differential Equations" published by university of Tabriz, Iran.