How to reference sources when I only took the ideas? I am writing my essay where I analyze how different text search algorithms work and compare their efficiency in specific situations.

I did not actually take even a sentence from where I have read about the algorithms, everything is written by myself, how I understood it, but of course I did not invent those algorithms, and I want (and I think this is a compulsory) to actually refer to those sources, but how do I do it? Should I simply create a footnote even though my essay does not contain any sentence from that source? My essay is going to be passed to some plagiarism checker, therefore, I do not want any problems with "fake footnotes just to make my essay look stronger" or something like that. We use ISO 690 citing style.
You should make it clear in the text who invented the algorithms, and cite next to the names, usually. Write something like:


  The XYZ search algorithm [1], works by...
  
  Foo et al. [2] propose an algorithm which...