.NET Hello world example does not work

using Couchbase.Core;

using Couchbase.Core.Buckets;

internal class Program

{

    private static readonly Cluster Cluster = new Cluster();

    private static void Main(string[] args)

    {

        using (var bucket = Cluster.OpenBucket())

        {

            var document = new Document<dynamic>

            {

                Id = "Hello",

                Content = new

                {

                    name = "Couchbase"

                }

            };

            var upsert = bucket.Upsert(document);

            if (upsert.Success)

            {

                var get = bucket.GetDocument<dynamic>(document.Id);

                document = get.Document;

                var msg = string.Format("{0} {1}!", document.Id, document.Content.name);

                Console.WriteLine(msg);

            }

            Console.Read();

        }

    }

}

Error	1	The type or namespace name 'Cluster' could not be found (are you missing a using directive or an assembly reference?)	c:\users\dave\documents\visual studio 2013\Projects\ConsoleApplication1\ConsoleApplication1\Program.cs	12	29	ConsoleApplication1