You can use following code snippet for book navigation block in your module/theme if you want to hide the links that are not of the page's language.

One of your most difficult jobs as a site administrator is soliciting inbound links to boost your traffic and your search engine position. Deep links, in context, are the most valuable.

Using the 'Path of Least Resistance' philosophy, provide users with link text at the bottom of every page using the following code snippet (D7) in a block.