View links, which is the most optimal for building an external reference mass promoted website.
It is assumed that eternal links are placed on donor sites forever, that is, “forever” or until the end of its existence.
The most convenient way to get eternal links is link exchanges, that make it possible to select donor sites taking into account all the required qualities (subject, authority, age etc.).
From the perspective of search engines, eternal links look more natural, than temporary. Their use is safer to advance.