The C11 Standard
- ISO/IEC 9899:2011 (C11), available for purchase from a member body of ISO or IEC or download the freely available most recent C11 draft — n1570.pdf.
Links that I’ve found to be generally of high quality
Good books
- The C Programming Language (2nd ed.) by Brian W. Kernighan and Dennis M. Ritchie. ISBN 0-13-110362-8.
- C: A Reference Manual (5th ed.) by Samuel P. Harbison, Guy L. Steele Jr. ISBN 0-13-089592X.
- C Programming: A Modern Approach (2nd ed.) by K. N. King. ISBN 0-393-96945-2.