Changes

* [[Timeline of pollution]] (expand):

** The economics of pollution (in particular, discussion of the concept of externalities, tragedy of the commons)

* [[Timeline of mobile telephony]] (expand):

** Voice over IP calling

* [[Timeline of Wi-Fi]] (expand):

** Wi-Fi calling (for both timelines) ✔

** tethering and hotspots created by mobile phones are worth mentioning, maybe in both timelines