Select specific html with "Html Agility pack"

I'm using html-agility-pack and trying to select out a specific html in it. The part I want to get is every GTIN-number in these blocks:

<td><span class="mobile-only">GTIN:</span>07330155011068</td>

-The part I want is the numbers after the ending span-tag. Ex: 07330155011068. Below is my html, and my c#-method:

<div class="table-wrapper" style='display: block;'>
    <table id="tableSearchArticle">
        <thead>
            <tr>
                <th><a href="#">Article</a></th>
                <th><a href="#">art.nr.</a></th>
                <th><a href="#">Brand</a></th>
                <th><a href="#">GTIN</a></th>
            </tr>
        </thead>
        <tbody>
            <tr>
                <td>
                    <a href="http://www.dabas.com/ProductSheet/Detail.ashx/121308" target="_blank">
                        Dalapannkaka fryst ca100st 6kg
                    </a>
                </td>
                <td><span class="mobile-only">Tillverkarens art.nr:</span>11068</td>
                <td><span class="mobile-only">Varumärke:</span>test</td>
                <td><span class="mobile-only">GTIN:</span>07330155011068</td>
            </tr>
            <tr>
                <td>
                    <a href="http://www.dabas.com/ProductSheet/Detail.ashx/124494" target="_blank">
                        Dessertpannkaka fryst ca100st 6kg
                    </a>
                </td>
                <td><span class="mobile-only">Tillverkarens art.nr:</span>11405</td>
                <td><span class="mobile-only">Varumärke:</span>test</td>
                <td><span class="mobile-only">GTIN:</span>07330155114059</td>
            </tr>
        </tbody>
    </table>

    </div>

And I'm using this method to trying to get my values. The problem is I don't know what code to write in the SelectNode() to get the innerHtml containing the GTIN-numbers.

public void TestGetHtml()
    {
        var doc = new HtmlDocument();
        doc.Load("C:/Users/Desktop/test.html");
        foreach (HtmlNode link in doc.DocumentNode.SelectNodes("TODO: Add code to select all GTIN"))
        {

        }
        doc.Save("file.htm");
    }