GoogleAPI in VisualStudio

I'm trying to implement over a ready-made class that sent me using GoogleAPI, but I can not in any way add the reference to the project via NuGet. Do you know where I can download it? Here is the code:

using System.Collections.Generic;

using System.IO;

using System.Net;

using GoogleAPI.Maps.Model; // Esta daqui

using GoogleAPI.Maps.Model.Geocoding; // Esta daqui também

using Newtonsoft.Json;

namespace CepApp

{
    public class AddressUtil

    {

        public class Location
        {
            public double lat { get; set; }
            public double lng { get; set; }
        }

        public class Geometry
        {
            public Bounds bounds { get; set; }
            public Location location { get; set; }
            public string location_type { get; set; }
            public Viewport viewport { get; set; }
        }

        public class Result
        {
            public List<AddressComponent> address_components { get; set; }
            public string formatted_address { get; set; }
            public Geometry geometry { get; set; }
            public string place_id { get; set; }
            public List<string> types { get; set; }
        }


        public class RootObject
        {
            public List<Result> results { get; set; }
            public string status { get; set; }
        }

        public static RootObject GetLatLongByAddress(string address)
        {
            var root = new RootObject();

            var url =
                string.Format(
                    "http://maps.googleapis.com/maps/api/geocode/json?address={0}&sensor=true_or_false", address);
            var req = (HttpWebRequest)WebRequest.Create(url);

            var res = (HttpWebResponse)req.GetResponse();

            using (var streamreader = new StreamReader(res.GetResponseStream()))
            {
                var result = streamreader.ReadToEnd();

                if (!string.IsNullOrWhiteSpace(result))
                {
                    root = JsonConvert.DeserializeObject<RootObject>(result);
                }
            }
            return root;
        }
    }
}

Reinforcing: The class was already implemented in another project, but I can not add the reference to mine.

Thank you!