Core.PhonewordTranslator.ToNumber compilation error

System

Microsoft Visual Studio Premium 2013 Version 12.0.21005.1 REL Microsoft .NET Framework Version 4.5.51641

Xamarin.Android 4.10.02014 (4b53fbd0) Visual Studio plugin to enable development for Xamarin.Android.

Xamarin.iOS 1.10.39 (e0334707)

Visual Studio extension to enable development for Xamarin.iOS

Application

Created an "Android Application" using visual studio wizard

Problem

Trying to use Core.PhonewordTranslator.ToNumber in the main activity

I get compilation error

"The name 'Core' does not exist in the current context".