Dear R experts, I have started recoding bottlenecks of my R program in C. When doing so, I realized that my C knowledge is a bit rusty: the last time I used (or dabbled in) this language was 12 years ago, and I seem to have forgotten quite a bit, and the language also evolved since. Please recommend books for brushing up on my C knowledge, if possible, ones that are clear and use recent C like C99 (if you think that makes sense). I only expect to write 10-20 line routines to be called from R, but I think that having clear concepts and foundations would help me do it better. Thanks, Tamas