Link References
Link References accompany Links and Images, and are used to keep path values in a separated location from text content. They're useful for readability because they simplify links and images in inline text, and can be written in a standalone location for editing en masse.
This section requires familiarity with Links and Images to teach referencing concepts.
Syntax
A Link Reference must be the only thing on a line. The link key is written between [ and ]:. The URL path is written next, separated by a space. Optionally, a title can be written after the URL, separated by a space.
Once a Link Reference has been written, the link key from it can be used with a Link or Image. Replace the Link/Image's parenthesis () section with the link key between [ and ].
Basics
A Link Reference example used with an accompanying Link. The Link is written first and makes use of the link key, in this example 0.
[Link Text][0]

[0]: path/to/my_doc.md
Titles are optional. Keep the URL and title separate with a space.
[Link Text][0]

[0]: path/to/my_doc.md "Link Title"
A Link Reference example with an accompanying Image.
![alt text][0]

[0]: path/to/my_image.png
Make sure to keep the Reference on it's own line. The Link or Image can be used anywhere text is allowed, though.
For more info, check the [Link][0].

[0]: my_doc.md
Use Unique Values for Link Keys
Any text will work for the link key, but something unique that can be searched for will help in the authoring process. Link keys must be one-of-a-kind as well. In the case of overlapping link keys, the last link key written will be the accepted one.
[wwdoc_0001]: my_doc.md
[wwdoc_0002]: doc2.md
[wwdoc_0003]: doc3.md

[wwimg_0001]: img1.png
[wwimg_0002]: img2.png
[wwimg_0003]: img3.png
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