I came across a paper published in the Journal of Mathematical Physics in the year 2016. In the paper, the authors claimed to have developed a methodology which extends the dimension of an existing method. But this extension has already been discussed in a paper published in 2014. This seems to be a kind of cheating which the reviewers of journal failed to identify. The bibliography also appears to the suspicious as a large number of papers of a particular author has been cited without any motivation. I want to report this unscrupulous work, how can I report to the journal?
PS. This is not a case of plagiarism but a kind of unscrupulous research.