import re


def isssn(value):
    """
    Return whether or not given value is a U.S. Social Security Number.
    If the value is a U.S. Social Security Number, this function returns ``True``, otherwise ``False``.

    Examples::

        >>> isssn('191 60 2869')
        True

        >>> isssn('66690-76')
        False

    :param value: string to validate U.S. Social Security Number
    """
    ssn = re.compile(r'^\d{3}[- ]?\d{2}[- ]?\d{4}$')
    if value == '' or len(value) != 11:
        return False
    return bool(ssn.match(value))