Use HTTPS MDPI link and increase urlchecker timeout.

Makefile

@@ -64,6 +64,7 @@ lint: ## check style with flake8
 
 urlcheck: ## check for dead URLs
 	urlchecker check . \
+		--timeout 10 \
 		--file-types .py,.rst,.md,.json \
 		--white-listed-patterns www.enmap.org  # certificate checks fail although URLs work
 

docs/algorithm_descriptions.rst

@@ -130,7 +130,8 @@ Co-Registration Software for Multi-Sensor Satellite Data. Remote Sensing. 2017;
 In EnPT, AROSICS is used to automatically compute thousands of tie points between a selected EnMAP band the
 user-provided reference image. The computed shifts are considered in the orthorectification step.
 
-__ https://doi.org/10.3390/rs9070676
+__ https://www.mdpi.com/2072-4292/9/7/676
+
 
 
 .. VNIR/SWIR coregistration estimation???