Dear Anton Georgiev,

A digital object identifier (DOI) is a unique alphanumeric string assigned by a registration agency (the International DOI Foundation) to identify content and provide a persistent link to its location on the Internet. The publisher assigns a DOI when your article is published and made available electronically.

Unfortunately, some researchers still not know the efficient of DOI in citation and recall a paper from the index of search engines. I guess the DOI should be the primary key of research any article. 

Best regards,

Musab Tr

I think it depends on the awareness of some publishers about the importance of DOI for modern indexing services.

Regards

SM Najim

 I agree with Salah , so you can see this paper for more information about DOI:

http://www.apastyle.org/manual/related/electronic-sources.pdf

You are absolutely right, but however I can not explain myself uninformed of these publishers about the importance of DOI. All major search engines work with DOI.

Professor Salah Mahdi Najim, Thanks for your opinion

regards

Anton Georgiev

Dear Anton Georgiev,

A digital object identifier (DOI) is a unique alphanumeric string assigned by a registration agency (the International DOI Foundation) to identify content and provide a persistent link to its location on the Internet. The publisher assigns a DOI when your article is published and made available electronically.

Unfortunately, some researchers still not know the efficient of DOI in citation and recall a paper from the index of search engines. I guess the DOI should be the primary key of research any article. 

Best regards,

Musab Tr

Professor Saeed Al Rashid thanks for the attached article. The article is interesting and useful.

With respect

Anton Georgiev

A digital object identifier (DOI) is a unique alphanumeric string assigned by a registration agency (the International DOI Foundation) to identify content and provide a persistent link to its location on the Internet. The publisher assigns a DOI when your article is published and made available electronically.

All DOI numbers begin with a 10 and contain a prefix and a suffix separated by a slash. The prefix is a unique number of four or more digits assigned to organizations; the suffix is assigned by the publisher and was designed to be flexible with publisher identification standards.

We recommend that when DOIs are available, you include them for both print and electronic sources. The DOI is typically located on the first page of the electronic journal article, near the copyright notice. The DOI can also be found on the database landing page for the article.

good luck

Here I found a lot of useful information.

dear Professor Hiba Riyadh Jameel

Thank you for your valuable opinion on the matter.

With great respect

Anton Georgiev

Dear Professor Margreta Vassileva

Thank you for your valuable opinion on the matter.

I'm glad to know that the information here was useful to you.

With great respect

Anton Georgiev

dear

i agree with Dr. Salah Mahdi Najim opinion

regards 

Dear Anton Georgiev,

Some of the publishers do not assign a DOI when our article is published due to many reasons. Few of them are shown below:

1. The search engine has numerous problems discovering & retrieving documents due, in part, due to the enormous size of the Web.

2. The transience of Web sites coupled with the difficulty of discovering & retrieving their contents, causes serious problems for libraries and other institutions that attempt to integrate Web documents into their local systems.

3. Many of the URLs found in databases such as online catalogs are no longer valid.

4. The majority of users have been conditioned to believe that most things on the Internet (especially text) should be free.

5. Most of the problems with the Internet was due to the function of the URL, which was never meant to be an identifier but only to designate the location of objects.

6. There are still some technical problems associated with adding digital watermarks to text objects.

7. Since the biggest problems with URL stability and the lack of persistence of Internet objects lies outside the products provided through large publishers, it is unclear how the DOI System is going have any beneficial effect on the solution of the Internet's problems.

I hope I have answered your question.

With Best Wishes,

Samir G. Pandya