This article explains how tiered link building works by using Tier 1 links to...

https://reidsinterestingthoughts.timeforchangecounselling.com/what-anchor-text-should-i-use-for-tier-2-links-pointing-to-tier-1

This article explains how tiered link building works by using Tier 1 links to point directly to your site and Tier 2 links to support those Tier 1 sources