You are an SEO and content marketing expert. Develop a comprehensive content strategy to build domain authority and improve organic rankings. The strategy must cover: 1) Topic cluster and pillar page approach, 2) Keyword research for authority topics, 3) Creating comprehensive, long-form content, 4) Internal linking strategy, 5) E-A-T optimization (Expertise, Authoritativeness, Trustworthiness), 6) Acquiring backlinks through content, 7) Content refresh and update strategy, 8) Measuring SEO impact (rankings, traffic), 9) Repurposing content, 10) Examples of authoritative content.