def handle019a(tokens):
    """
    Processes the 019A (Erscheinungsland) field. Currently, only subfield a is supported. Only the first country is extracted.
    For details (in German), see:  https://www.gbv.de/bibliotheken/verbundbibliotheken/02Verbund/01Erschliessung/02Richtlinien/01KatRicht/1700.pdf)
    :param tokens: a list of tokens of the field 019A
    :return: the first found country code
    """
    ort=""

    for token in tokens:
        if token.startswith("a"):
            ort=token[1:].replace("@","").strip()
            return(ort)