Canonical SEO Content syndication plugin adds rel=canonical tag for content syndication. The meta box is added at edit post section.

ben.moody

Content Syndication Toolkit Reader

Allows clients to subscribe to content created using the 'Content Syndication Toolkit' plugin.

PublisherDesk

The Publisher Desk – Headlines Plus Widget

Headlines Plus: Free plugin for WordPress to grow your audience with traffic sharing, syndication, and lazy-loading widgets or shortcodes.

Content Syndication Toolkit

Content Syndication Toolkit allows you to syndicate content to multiple client sites automatically. Posts, Categories, Tags, and Images.

Harsh Agrawal

Content syndication is a process of amplifying your content to other blogs without hurting the SEO of your original content. You can let other blogs to republish your content in exact format with rel=canonical tag.
You can read about Rel=canonical tag here at pt.4: https://support.google.com/webmasters/answer/139066?hl=en
In this guide you can learn everything about using content syndication for content marketing: http://www.shoutmeloud.com/relcanonical-wordpresss-content-syndication-seo.html
Canonical SEO Content syndication plugin adds a meta box at post editor section. You can add permalink of post where the content was originally published. Popular blogs like bufferblog, readwriteweb are taking advantage of content syndication and rel=canonical tags.

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