diff --git a/paper/main.bib b/paper/main.bib
index dd329d01ac3b0debfa11d0251ff7d4195420e4e8..02a9448281606b3707fffe5edb5624982761527c 100644
--- a/paper/main.bib
+++ b/paper/main.bib
@@ -16,7 +16,7 @@ year={2009},
 volume={10}, 
 number={1}, 
 pages={4-21}, 
-doi={10.1109/TITS.2008.2011712}, 
+mask_doi={10.1109/TITS.2008.2011712}, 
 ISSN={1524-9050}, 
 month={March},}
 
@@ -45,7 +45,7 @@ month={March},}
   isbn={9780890067932},
   lccn={95049984},
   series={Artech House telecommunications library},
-  url={https://books.google.it/books?id=5OYInwEACAAJ},
+  mask_url={https://books.google.it/books?id=5OYInwEACAAJ},
   year={1996},
   publisher={Artech House}
 }
@@ -60,8 +60,8 @@ month={March},}
  location = {Beijing, China},
  pages = {335--344},
  numpages = {10},
- url = {http://doi.acm.org/10.1145/2030112.2030158},
- doi = {10.1145/2030112.2030158},
+ mask_url= {http://doi.acm.org/10.1145/2030112.2030158},
+ mask_doi= {10.1145/2030112.2030158},
  acmid = {2030158},
  publisher = {ACM},
  address = {New York, NY, USA},
@@ -77,7 +77,7 @@ volume={},
 number={},
 pages={18-26},
 keywords={Global Positioning System;smart phones;software based duty cycling;trajectory based services;smartphone apps;route accuracy;map matching;path construction algorithm;smartphone GPS receiver;Global Positioning System;Roads;Databases;Energy consumption;Conferences;Google;Image color analysis},
-doi={10.1109/CCNC.2016.7444725},
+mask_doi={10.1109/CCNC.2016.7444725},
 ISSN={2331-9860},
 month={Jan},}
 
@@ -93,8 +93,8 @@ month={Jan},}
  location = {San Francisco, California, USA},
  pages = {315--330},
  numpages = {16},
- url = {http://doi.acm.org/10.1145/1814433.1814464},
- doi = {10.1145/1814433.1814464},
+ mask_url= {http://doi.acm.org/10.1145/1814433.1814464},
+ mask_doi= {10.1145/1814433.1814464},
  acmid = {1814464},
  publisher = {ACM},
  address = {New York, NY, USA},
@@ -113,8 +113,8 @@ month={Jan},}
  location = {San Francisco, California, USA},
  pages = {285--298},
  numpages = {14},
- url = {http://doi.acm.org/10.1145/1814433.1814462},
- doi = {10.1145/1814433.1814462},
+ mask_url= {http://doi.acm.org/10.1145/1814433.1814462},
+ mask_doi= {10.1145/1814433.1814462},
  acmid = {1814462},
  publisher = {ACM},
  address = {New York, NY, USA},
@@ -132,8 +132,8 @@ month={Jan},}
  location = {Berkeley, California},
  pages = {85--98},
  numpages = {14},
- url = {http://doi.acm.org/10.1145/1644038.1644048},
- doi = {10.1145/1644038.1644048},
+ mask_url= {http://doi.acm.org/10.1145/1644038.1644048},
+ mask_doi= {10.1145/1644038.1644048},
  acmid = {1644048},
  publisher = {ACM},
  address = {New York, NY, USA},
@@ -151,8 +151,8 @@ month={Jan},}
  location = {Krak\&\#243;w, Poland},
  pages = {221--234},
  numpages = {14},
- url = {http://doi.acm.org/10.1145/1555816.1555839},
- doi = {10.1145/1555816.1555839},
+ mask_url= {http://doi.acm.org/10.1145/1555816.1555839},
+ mask_doi= {10.1145/1555816.1555839},
  acmid = {1555839},
  publisher = {ACM},
  address = {New York, NY, USA},
@@ -170,8 +170,8 @@ month={Jan},}
  location = {Krak\&\#243;w, Poland},
  pages = {179--192},
  numpages = {14},
- url = {http://doi.acm.org/10.1145/1555816.1555835},
- doi = {10.1145/1555816.1555835},
+ mask_url= {http://doi.acm.org/10.1145/1555816.1555835},
+ mask_doi= {10.1145/1555816.1555835},
  acmid = {1555835},
  publisher = {ACM},
  address = {New York, NY, USA},
@@ -213,7 +213,7 @@ volume={},
 number={},
 pages={2716-2720},
 keywords={Global Positioning System;mobile computing;wireless LAN;EnLoc;energy-efficient localization;mobile phones;location-based applications;GPS;WiFi;GSM;Energy efficiency;Mobile handsets;Global Positioning System;GSM;Batteries;Energy measurement;Wireless sensor networks;Costs;Poles and towers;Communications Society},
-doi={10.1109/INFCOM.2009.5062218},
+mask_doi={10.1109/INFCOM.2009.5062218},
 ISSN={0743-166X},
 month={April},}
 
@@ -229,8 +229,8 @@ month={April},}
  pages = {2:1--2:7},
  articleno = {2},
  numpages = {7},
- url = {http://doi.acm.org/10.1145/2676727.2676729},
- doi = {10.1145/2676727.2676729},
+ mask_url= {http://doi.acm.org/10.1145/2676727.2676729},
+ mask_doi= {10.1145/2676727.2676729},
  acmid = {2676729},
  publisher = {ACM},
  address = {New York, NY, USA},
@@ -248,8 +248,8 @@ month={April},}
  location = {Barcelona, Spain},
  pages = {61--62},
  numpages = {2},
- url = {http://doi.acm.org/10.1145/1592606.1592621},
- doi = {10.1145/1592606.1592621},
+ mask_url= {http://doi.acm.org/10.1145/1592606.1592621},
+ mask_doi= {10.1145/1592606.1592621},
  acmid = {1592621},
  publisher = {ACM},
  address = {New York, NY, USA},
@@ -266,7 +266,7 @@ volume={},
 number={},
 pages={155-166},
 keywords={compressed sensing;Global Positioning System;radio receivers;synchronisation;compressed sensing;visible satellites;sparse acquisition information;sparse approximation;data offloading operation;energy cost;delay-tolerant applications;energy efficient GPS sensing;low-cost receivers;sparse-GPS;energy efficient GPS acquisition;Global Positioning System;Satellites;Dictionaries;Sensors;Receivers;Satellite broadcasting;Approximation methods;GPS;synchronization;location sensing;energy efficiency;sparse approximation;compressed sensing},
-doi={10.1109/IPSN.2014.6846749},
+mask_doi={10.1109/IPSN.2014.6846749},
 ISSN={},
 month={April},}
 
@@ -281,8 +281,8 @@ month={April},}
  location = {Istanbul, Turkey},
  pages = {353--364},
  numpages = {12},
- url = {http://doi.acm.org/10.1145/2348543.2348587},
- doi = {10.1145/2348543.2348587},
+ mask_url= {http://doi.acm.org/10.1145/2348543.2348587},
+ mask_doi= {10.1145/2348543.2348587},
  acmid = {2348587},
  publisher = {ACM},
  address = {New York, NY, USA},
@@ -300,8 +300,8 @@ month={April},}
  location = {Tokyo, Japan},
  pages = {182--186},
  numpages = {5},
- url = {http://doi.acm.org/10.1145/3029387.3029408},
- doi = {10.1145/3029387.3029408},
+ mask_url= {http://doi.acm.org/10.1145/3029387.3029408},
+ mask_doi= {10.1145/3029387.3029408},
  acmid = {3029408},
  publisher = {ACM},
  address = {New York, NY, USA},
@@ -318,7 +318,7 @@ volume={},
 number={},
 pages={75-78},
 keywords={Global Positioning System;ionospheric disturbances;ionospheric electromagnetic wave propagation;radiowave propagation;space weather impact;GPS ionospheric delay;physical-chemical processes;magnetic-ionospheric conditions;electromagnetic waves propagation;satellite positioning systems;solar activity;Global Positioning System;Delay;Sun;Earth;Ionosphere;Geomagnetism;Satellite broadcasting;Wind;Electronic mail;Chemical processes;space weather;ionospheric disturbances;GPS ionospheric delay},
-doi={10.1109/ELMAR.2007.4418803},
+mask_doi={10.1109/ELMAR.2007.4418803},
 ISSN={1334-2630},
 month={Sept},}
 
diff --git a/paper/sections/06-results.tex b/paper/sections/06-results.tex
index b047e4bcf344b9d9792a72413a05995f02b33c39..1ca81b2adb4da66404e0910e39285fb1a9303fd7 100644
--- a/paper/sections/06-results.tex
+++ b/paper/sections/06-results.tex
@@ -3,7 +3,7 @@
 \begin{groupplot}[%
  group style = {group size = 1 by 2, vertical sep = 0.2cm,
  xlabels at=edge bottom,xticklabels at=edge bottom,},
- height = 2.5cm,
+ height = 2.7cm,
  grid style = {black!30, dashed},
  grid = major,
  width = 0.9\columnwidth,
@@ -55,7 +55,7 @@ experiment with the accuracy-battery trade-off.
 \begin{groupplot}[%
  group style = {group size = 1 by 2, vertical sep = 0.2cm,
  xlabels at=edge bottom,xticklabels at=edge bottom,},
- height = 2.5cm,
+ height = 2.7cm,
  grid style = {black!30, dashed},
  grid = major,
  width = 0.9\columnwidth,
@@ -85,7 +85,7 @@ experiment with the accuracy-battery trade-off.
 \begin{groupplot}[%
  group style = {group size = 1 by 3, vertical sep = 0.2cm,
  xlabels at=edge bottom,xticklabels at=edge bottom,},
- height = 2.5cm,
+ height = 2.7cm,
  grid style = {black!30, dashed},
  grid = major,
  width = 0.9\columnwidth,