The main content is visible in the middle and the related content is displayed in parallel on the side
The connections between the different sources are displayed with colored lines between the documents
To see the related source, click on it with your mouse. To get back to the prior source, click on it.
About the document:
The document, written by Moe Justes, is a compilation of different sources.
I haven’t read all the content; but though Ted Nelson has said he himself is an atheist, Juste’s method of intertextually invoking other sources is actually quite biblical.
At this point, it probably isn’t easy to duplicate something like this with your own content, but I wonder how biblical criticism could benefit from this form of parallel writing.