Problem with PubMed connector

A few days ago, I noticed that Pubmed Citation Database Connector seemed to have stopped working. After looking into NCBI website (, I realized the cause may be that NCBI blocked my IP.

In Setup, step 3, when editing Pubmed Citation Database Connector, there is an option for you to enter “PubMed Registration Email”. But I don’t know what email I should type in. According to NCBI Use the E-utility URL page, I see this statement: "The value of email should be a complete and valid e-mail address of the software developer and not that of a third-party end user. ". I understand that only OJS can register an email with NCBI, but individual users of OJS.

Also, i have this setting in file citation_checking_max_processes = 8

Could someone let me know how to solve this issue? If needed, can users of OJS register with NCBI? Thank you in advance.

Hi @newbies,

See e.g. this thread:

Alec Smecher
Public Knowledge Project Team