Finding the thumbnail tags

[khanxc]

How to find the cover image tag for different news feeds on the fly?
In the framework this line

 let imgURL: NSURL? = NSURL(string: projectURL + "/cover_image?style=200x200#")

And i tried for theGuardian.com with this

var projectURL = "http://www.theguardian.com/world/2015/dec/29/mystery-of-emergency-landings-of-qatari-royal-planes-in-switzerland"
let imgURL: NSURL? = NSURL(string: projectURL + "#img-1")

And not successful, still showing placeholder image, where am i going wrong?