loadJSON & loadJSONObject returning "not a function" error

We copied the sample code from the JSON Support|Autoloading from XML sample but are getting an error that loadJSON is not a function. We then attempted to use the loadJSONObject with same command used in the JSON Support|Different Loading Modes sample and got an error that loadJSONObject is not a function. The dhtmlxtree_json.js has been sourced in the code. Is there any additiona setup we’re missing?

Please double-check that ext/dhtmlxtree_json.js file included in your project, there is no any special actions necessary, except including that file.
If file including both

must be available