Update README.md

@@ -44,4 +44,4 @@ For training a new model set the list of parameters at `model_params_binClass.co
 $ python filter_abstracts_binClass.py --classA data/ecoli_abstracts/not_useful_abstracts.txt --classB data/ecoli_abstracts/useful_abstracts.txt
 $ python filter_abstracts_binClass.py --classA data/ecoli_abstracts/not_useful_abstracts.txt --classB data/ecoli_abstracts/useful_abstracts.txt
 ```
 ```
 
 
-where `--classA` and `--classB` (the useful papers) are used to specify input training files. In this example `data/ecoli_abstracts/useful_abstracts.txt` is the training files containing abstracts of papers reporting experimental data (the desired or useful class for us).
+where `--classA` and `--classB` (the useful papers) are used to specify input training files. In this example `data/ecoli_abstracts/useful_abstracts.txt` is the training file containing abstracts of papers reporting experimental data (the desired or useful class for us). This file must be parsed and it has a special format (the same thing holds for unuseful abstracts. See their contents).