[grovulent]

I developed them myself.

Mostly this doesn't add much overhead to the learning process. As I'm working through a math's text book (in ebook or pdf form) I use the windows 7 snipping tool to create two images - one of the question and solution. And then I just insert these into my card program. This takes about 15-30 seconds at the most.

I use mnemosyne as my repetition software which allows me to insert images - and I can also annotate my cards with latex. I have a number of latex macros set up on my keyboard so that I've become pretty quick at inputting latex.

I continue to annotate my cards as I progress. For a complex problem, what starts out as a simple cut and paste from a text book grows into a voluminous set of notes covering every aspect of the problem that I've had trouble with on different repetitions of the problem. These notes become what I use to create the smaller cards.

For abstract and complex material - there is no substitute for creating your own cards imo. You need to read through a text book anyway to ensure that there is no important context that you've missed. And it isn't much overhead to create your base set of cards, cutting and pasting as you go. But your gaps in understanding are your own - and only you can identify those and fill them.