According to Google, the results are ranked algorithmically based on many signals that look for quality and in-depth content. Google also gives recommendations on helping Google algorithms understand pages:
- use schema.org “article” markup,
- provide authorship markup,
- rel=next and rel=prev for paginated articles (also watch out for common rel=canonical mistakes),
- provide information about your organization’s logo,
- and of course, create compelling in-depth content.
Google in a separate blog says: “To understand a broad topic, sometimes you need more than a quick answer. Our research indicates perhaps 10% of people’s daily information needs fit this category -- topics like stem cell research, happiness, and love, to name just a few. That's why over the next few days we’ll be rolling out a new feature to help you find relevant in-depth articles in the main Google Search results.”