def external_question_xml(question_url):
    """Return AMT-formatted XML for external question.

    See: https://docs.aws.amazon.com/AWSMechTurk/latest/AWSMturkAPI/
    ApiReference_ExternalQuestionArticle.html
    """
    question_xml = (
        '<?xml version="1.0" encoding="UTF-8"?>'
        '<ExternalQuestion xmlns="http://mechanicalturk.amazonaws.com/'
        'AWSMechanicalTurkDataSchemas/2006-07-14/ExternalQuestion.xsd">'
        '<ExternalURL>{0}</ExternalURL>'
        '<FrameHeight>0</FrameHeight>'
        '</ExternalQuestion>'
    ).format(question_url)
    return question_xml