It wouldn't be the World Wide Web without links between websites, resources, and services. Crediting resources for their work is something we highly recommend doing within your Guides. Providing a link to services you mention, content you wish to disseminate, or videos and images you've included in your content is something you should get into the habit of doing.
We've built plenty of tools for linking both internally to content you've created in a Guide, and externally to content around the internet.
All content sections within a Guide have the WYSIWYG editing bar (it's black, and hovers as you scroll through your content). In that bar, there exists a "Link" tool to help you link to content. You can use it to both link, and unlink text within your Guide:
Note: Do not remove, or edit, the URL or text that is auto-generated in this situation.
It's pretty easy to add a link to an outside resource for your Guide:
Be sure to add as many links as possible to any helpful blog posts, websites, tools, and resources your readers may find interesting. Links are an easy way to add utility to a Guide.