Merge pull request #3315 from andrefaraujo/master

Small updates to DELF markdown files: dataset location and small troubleshooting fix.

research/delf/EXTRACTION_MATCHING.md

@@ -62,6 +62,6 @@ The image `matched_images.png` is generated and should look similar to this one:
 
 `matplotlib` may complain with a message such as `no display name and no
 $DISPLAY environment variable`. To fix this, one option is add the line
-`backend : Agg` to the file `config/matplotlib/matplotlibrc`. On this problem,
+`backend : Agg` to the file `.config/matplotlib/matplotlibrc`. On this problem,
 see the discussion
 [here](https://stackoverflow.com/questions/37604289/tkinter-tclerror-no-display-name-and-no-display-environment-variable).

research/delf/README.md

@@ -72,9 +72,11 @@ feature extraction and matching:
 
 ## Dataset
 
-The Google-Landmarks dataset will be released together with a Kaggle-hosted
-landmark recognition competition. We will include the link to it here once it is
-launched (expect this to be done around mid-January, 2018).
+The Google Landmarks dataset has been released as part of two Kaggle challenges:
+[Landmark Recognition](https://www.kaggle.com/c/landmark-recognition-challenge)
+and [Landmark Retrieval](https://www.kaggle.com/c/landmark-retrieval-challenge).
+If you make use of the dataset in your research, please consider citing the
+paper mentioned above.
 
 ## Maintainers