One of the topics that is at the top of my list to gain a better understanding of is Linear Programming. Before my mother's death last year derailed my studies, I was working through my Operations Research class, and honestly treading water more than anything. I could understand the material, and doing alright with problem sets, but I felt like I needed something more at a basic level.
In hoping to continue my official studies this coming Spring, I've decided to do some independent studies of topics related to Operations Research. I'm beginning with Linear Programming, and have compiled a short list of resources I've discovered online. I hope that you'll find this list of free texts helpful in your own studies. They all come vetted from various sites, including MathExchange and its related domains.
