What are the functions of the following C libraries? nr.h nrutil.h What I understood is that these are used when u are calling functions like 'qromb or polint or trapzd' for integration. Acutally when I compile the program I get these errors. nr.h: No such file or directory nrutil.h: No such file or directory I searched in net , but cant fix it. How can I add those libraries?