Self-citation (giving proper reference) is quiet normal. See also these discussions:

https://www.researchgate.net/post/What_is_your_opinion_on_self-citation

https://www.researchgate.net/post/Can_i_use_my_previous_published_research_as_a_reference_for_my_new_research

https://www.researchgate.net/post/How_much_self-citations_affect_the_authors_credibility

https://www.researchgate.net/post/Is_Self-Citation_considered_as_a_type_of_plagiarism

https://www.researchgate.net/post/Self_citation_in_research

https://www.researchgate.net/post/SELF_CITATION_Is_it_against_the_ethics_of_research

https://www.researchgate.net/post/Citation-of-own-work

https://www.researchgate.net/post/What_are_the_top_journals_attitudes_toward_self-citations

https://www.researchgate.net/post/How_does_self_citation_affect_your_academic_profile

https://www.researchgate.net/post/Is_self-citation_functioning_in_the_same_way_as_any_cited_reference_appended_to_a_paper

https://www.researchgate.net/post/Is_it_bad_to_self_cite

https://www.researchgate.net/post/What_are_the_dangers_of_self-citations

The important issue is not disclosure, but that publication of such work would be redundant. The previously published material remains in the public domain and is generally subject to copyright. Discussion of the work is, of course, acceptable, but not replication of whole sentences or paragraphs, verbatim.

There may also be a question of breach of copyright and the editor might want to remind the author of copyright law.

Like many before, most self citations have positive and negative aspects. Basically self citation is like any other citation but with a motive or more. It can be viewed as self promotion but it also can be viewed as a spin and different approach to the same material. The problem is the two cannot be diagnosed that easily and there is no academic police. While one can be suspected of self promotion it can not be proven . Furthermore, there is no objective mechanism to do so and it is discouraged by most journals. I like to cite my work because I have a different view on the material or I believe that made a breakthrough which must be mentioned. For instance, in the area ship stability, discussion on the ship rotation can not be done or understood without understanding the mechanism around what point the ship is rotating around. Since I pioneered this area I cannot see any real discussion on the topic of ship rotation without a discussion my discoveries by me or any serious person in the field. The need of recitation (literature review) is important for new people who just introduce to the field and general readability.

The above discussion also raisea the point of avoiding mentioning others works just to bury or drawn it out. This action is done in indirectly as way to be self promotion. I have encountered this action much more often. This also done in the general by press by organizations like CNN, BBC and MSNBC etc. They hope by not mentioning a work, it will be dissipated. It is common done by the establishment individuals. The interesting point that this might have stronger consequence For example, in die casting . The establishment group in Ohio state university attempt to cover the discovery of critical vent area (which I discovered) and now some people having/writing papers that are simply erroneous.

Hello Raju Vaishya

More often than not, if I use self-citation, it is to clearly say that "I am an expert on this topic and this is my opinion". In those cases, it is not usually a worry that the work/publication is "redundant" as you say. If anything, it is a form of the term that Genick Bar-Meir used that it is "self promotion". I hope this is the most positive way to use such a method.

I feel that the self-citations should not more than 5-10% in any paper. More so, one cannot use the same text language or figures/tables etc. in the paper (verbatim), even from your prior publication. As this violate the copyrights of the publisher, who own the rights of your published work (& not yourself any more).

I agree with Raju Vaishya sir. But generally self citation is 5 to 10% only. Furthermore, that is also from peer reviewed published articles. So that should be acceptable.

Quotation of information, both qualitative (sentence(s), clauses) and quantitative (data values), and paraphrasing of sentence(s), clauses, and so on, are two methods of using information in the literature to support or confirm the results in the literature; they are also methods of beginning a new work in accordance with pedagogical principles, from the known to the unknown where applicable. Quoting verbatim in only one or two instances is easier than paraphrasing. Most equations (e.g., the Arrhenius equation) used in the literature are quotations because they were not modified. Thus, using equations that are a modification of original equations or exactly the original equation (verbatim) without reference to the authors of such equations for whatever reason is extremely unethical. A violation of ethics becomes a serious issue if the correct reference is not given. Some professors have resigned for failing to cite the information in the literature with references. The burning issue is that some authors only cite reference materials based on personality, nationality, "highest bidder," and so on; this is equivalent to saying that first-class degrees are only awarded to people from wealthy families! Racism has always been a monster that must be destroyed.

It is an unnecessary distraction to question a quotation that has been duly cited with reference and without discrimination. This is the only issue of primary concern—unacceptable plagiarism.

Hello, again, Raju Vaishya

Interesting that you suggested 5-10% (which was also the range suggested by Munish Sood ). I've seen some journals say the limit is 20% or something like that - does that show those journals are more "desperate" and have lower standards?

Self-citation may substantially affect a journal’s IF compared with IFs of other journals in the same specialty, self-citation is prone to manipulation and abuse, and the IF does not account for self-citation. Self-citation can bias how a journal is perceived but the bias can be overcome by ranking journals by self-citation-free indices.

"Charity begins at home!" If the works of other people should be cited (attributed or referenced), any new work or review where one's work is relevant must be cited and appropriately referenced, or else it will amount to self-plagiarism and unethical practices.

Should follow COPE Ethical Publishing Guidelines