ncnn/CONTRIBUTING.md

## Acknowledgements
- Thanks to bug1989 [https://github.com/bug1989] for contributing the initial quantized int8 inference code and a large variety of device benchmark
- Thanks to zhiliu6 [https://github.com/zhiliu6] for contributing the darknet conversion tool, operators and YOLO examples
- Thanks to Tijmen Verhulsdonck [https://github.com/Timen] for contributing the massive AVX optimization for x86 platform