Co-Citation is a term from search engine optimization. Search engines can recognize and establish the relationship between two websites when both link to a third website. Links between the first two websites are not necessary, only the common link to the third website.
The term co-citation refers to two quotations that authors use independently of each other and that come from the same source. Basically, a distinction is made between two forms of co-citation. The document citation describes the citation from classics and standard works which are cited as sources. In contrast, keywords that clearly describe a topic are used by different authors in their publications.
Co-Citation can be divided into three stages. The lowest is the CS-Co-Citation, where "CS" stands for "Common Sense". The point is that linked pages allow conclusions to be drawn about the quality of the linked document. In addition to the closeness to the topic, high quality plays a role. If a website links to another, high-quality site, there is a high probability that the linked site will also have high quality standards for itself.
The second stage is called Neighbourhood-Co-Citation. This offers more value, because the corresponding documents are linked not only once, but several times, and can be assigned to the same topic. Due to both the high quality and the increased linking, your own website gains in quality and is ranked better in the search engines. At this level of co-citation, linking your own site is not absolutely necessary for topic sizes. A thematic proximity to the high-quality pages is sufficient to develop advantages. In the next step, however, efforts should be made to link to the expert pages. Ultimately, it is a matter of being associated with as many expert pages as possible, which requires perseverance and a lot of work and is connected with deep insights into the corresponding topic.
The third and most demanding level is called Linkless Co-Citation. Those who reach this level do not need (new) links, only their own name stands for quality and is rewarded with attention by the search engines. If a particular name is often mentioned in relation to a particular topic and in documents classified as important and high quality, the search engines assume that this name has the appropriate relevance, and rank it well even if the links are missing. However, the path to Linkless Co-Citation is a long one, because until you reach the point where the name alone is sufficient to ensure a good ranking, numerous links have to be achieved. Because search engines initially react to links, only later can a name be the only program. Before joining the Linkless Co-Citation, it is therefore important to be branded and to achieve a certain degree of awareness by means of brand links.
As well as co-citation, co-occurrence also plays a role in search engine optimization. While co-citation describes the relationship between different websites, co-occurrence refers to certain terms. Therefore, if certain terms are often used together, it is assumed that there is a relationship between them. This coexistence of terms is then called co-occurrence.
It has been discussed for years whether co-citation and co-occurrence are effective in regards to search engine optimization. Although numerous experts and SEO experts have commented on this topic, there has not yet been a meaningful study.
Even though the effectiveness of co-citation or co-occurrence in regards to search engine optimization is not completely conclusive, it is not recommended to renounce other websites, whether out of egomania or because one wants to try to remain self-sufficient and independent. The principle of the Internet is to use the potentials and contents of other sites and thus also to offer readers added value (further links are often not only desired, but even demanded). On the other hand, expert status is most likely to be achieved if you join the ranks of other experts who also provide high-quality content on a subject. Those who claim to write high-quality articles must assume that readers also have a certain claim to quality and want to know where certain information comes from or from which other website is quoted.
To offer high-quality content, it is important and useful to link to further sources. A little co-citation should therefore be part of any search engine optimization. How intensively and professionally the described methods are applied is another question and depends on your own project. In order to make a name for oneself on a certain topic and to be well ranked, co-citation is recommended, despite the lack of meaningful studies.