Error when trying to retrieve Document Library in Sharepoint Hosted App using REST

Question

I have created the following REST request in order to retrieve the root folder of a Document Library added to a Sharepoint Hosted App
getProductDocumentFolder: function () {
$.ajax({
url: _spPageContextInfo.webServerRelativeUrl +
"/_api/web/GetFolderByServerRelativeUrl('/Lists/ProductDocuments')",
type: "GET",
headers: {
"accept": "application/json;odata=verbose",
success: function () {
alert("Success!");
//REST.Operator.readAll();
error: function (err) {
alert("Oops, error!");
alert(JSON.stringify(err));
The Document Library was added to the App from the Add > New Item menu in Visual Studio. I selected List and Selected Document Library from the Create a customizable list... dialog. The list is defined as shown in the picture below.
I get the generic error "Value does not fall within the excepted range".
I have tried both 
"/_api/web/GetFolderByServerRelativeUrl('/Lists/ProductDocuments')"
and
"/_api/web/GetFolderByServerRelativeUrl('/ProductDocuments')"
for the Document Library URL both I get the same error in both cases.
What am I missing here?

Answer 1

Problem solved. 
It turns out there should be NO leading '/' in the relative URL despite the example shown in http://msdn.microsoft.com/en-us/library/office/dn292553.aspx#Folders with "/Shared Folder".
The correct GetFolderByServerRelativeUrl-parameter in my case is 'Lists/Productdocuments'.
Unsure whether example is wrong or if it applies to other cases than mine.