Most search engine optimization professionals realize that citations (links) are a key aspect of optimizing a website for competitive placement on the search engines - and they aren't wrong.
In the case of Google, however, there's more to ranking a website than just the number and quality of inbound links - and we're not talking about site speed or information architecture.
SEO professionals optimizing a website for Google today (as well as in the past) are likely all too familiar with the concept of PageRank, which is Google's system of counting links to determine which pages are most important (and deserving of higher rankings).
There is another "factor" however that may play an equally important role in ranking but does not nearly get the attention it deserves, and it goes by the name of CheiRank.
While PageRank identifies very well-known and popular nodes, CheiRank highlights very "communicative" nodes. In essence, Google is not only measuring the quantity and quality of inbound links (elements that have been clearly demonstrated to influence PageRank), but also websites that communicate to other nodes via links on their own website (CheiRank).
How do these ranking mechanisms actually work? According to Wikipedia:
PageRank selects first articles on a broadly known subject with a large number of ingoing links while CheiRank selects first highly communicative articles with many outgoing links.
CheiRank will prove to be rather interesting to search engine optimization professionals, who have likely never previously come across the concept, as it clearly indicates that search engines do indeed consider far more than just links. In other words, providing well-developed, well-cited sources (content that links liberally outwardly) is another way to capture more organic/natural traffic from the search engines.