Similar to what the author has done, I wrote an open-source PHP application to manage "memes" I use in my writing. It's basically a bucket of ideas I've clipped from books, websites, etc (over 4,000 in the database now). I link the memes to their references, triple them into one-to-one relationships, and have "schemas" which are buckets of ideas I might use in articles and books I'm writing one day. I find it incredibly helpful in my personal use, but many people (understandably) find the interface a bit convoluted:
I have it on github, but if you like it, I would recommend rewriting it from scratch because I wrote this in the "Over-Engineering" phase of my career many years ago, over-using design patterns and abstracting away things to the point of making them incomprehensible. Also, I'm only maintaining it for my personal use now, but feel free to clone and make your own if you dare:
https://github.com/ideonexus/memexplex
Another great resource I would love to see made into something I could query for this is the public domain book "Fifteen Thousand Useful Phrases" by Grenville Kleiser.