Better link for Shannon Entropy and inclusion as informative reference

[ejratl]

Section 6.7.6.3 references the Shannon algorithm and links to a website. Specifies the calculated entropy for the section, as calculated using the Shannon algorithm (https://en.wiktionary.org/wiki/Shannon_entropy).

This is irregular, it should link to an informative reference that then links to a website. This particular link has no information on the topic nor on how to calculate the entropy, so a better reference should be selected (the original 1948 paper, perhaps).

[srrelitz2]

Here is a version of the 1948 paper -- https://web.archive.org/web/20130510074504/http://www.alcatel-lucent.com/bstj/vol27-1948/articles/bstj27-4-623.pdf