add ref

Author: seanghay

README.md

@@ -32,10 +32,17 @@ use crfs:Model;
 
 fn main() {
     let buf = fs::read("src/crf_ner_10000.crfsuite").unwrap();
-    let model = Model(&buf).unwrap();
+    let model = Model::new(&buf).unwrap();
     let input_str = "ឃាត់ខ្លួនជនសង្ស័យ០៤នាក់ Hello, world ករណីលួចខ្សែភ្លើង នៅស្រុកព្រៃនប់។".to_string();
     for token in khmercut::tokenize(&model, &input_str) {
         print!("{}|", token);
     }
 }
-```
+```
+
+---
+
+## References
+
+- [VietHoang1512/khmer-nltk/](https://github.com/VietHoang1512/khmer-nltk/) Khmer Natural Language Processing Tookit, Phan Viet Hoang (2020)
+- [seanghay/khmercut](https://github.com/seanghay/khmercut) A (fast) Khmer word segmentation toolkit.