Citation Hunt

The Wikipedia snippet below is not backed by a reliable source. Can you find one?

Click I got this! to go to Wikipedia and fix the snippet, or Next! to see another one. Good luck!

In page Interoperability:

"

North American freight and intercity passenger railroads are highly interoperable, but systems in Europe, Asia, Africa, Central and South America, and Australia are much less so. The parameter most difficult to overcome (at reasonable cost) is incompatibility of gauge, though variable gauge axle systems are increasingly used.[citation needed]