Update README.md

Author: neychev

README.md

@@ -37,6 +37,6 @@ Although if you don't have any of this, you could substitude it with your dilige
 
 A lot of great materials are available online. See [extra_materials.md](https://github.com/girafe-ai/ml-mipt/blob/master/extra_materials.md) file for the whole list.
 
-Informal "aggregation" of all topics by previous years students: [file](https://github.com/girafe-ai/ml-mipt/blob/spring_2019/ML_informal_notes.pdf) (in Russian) - useful for fast and furious exam passing.
+Informal "aggregation" of all topics by previous years students: [file](https://github.com/girafe-ai/ml-mipt/blob/master/ML_informal_notes.pdf) (in Russian) - useful for fast and furious exam passing.
 
 Also lectures and seminars contains references to more detailed materials on topics.