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For a math journal, after 4 weeks of submission, the status went from "with editor" to "reviewer invited", and its been in that particular state for the past 3 months. If you have any editorial experience, I'd like to know when would this kind of state happens, and does it say anything about the manuscript content, especially why the editor is finding hard to get the reviewers accept invitation, or is it that the reviewers for the subject matter of the paper, are rare to find?
Edit : more informtion
I have enquired. The Editorial Manager assured me that the Editor is carefully following and taking good care of the review process. What I have seen in earlier communication with Editor, I have no reason to doubt his interest in the manuscript. He seemed very much interested.