def processauthors_removeparen(authors_string):
    """Remove parentheses

    See docstring of processauthors() for more information.

    >>> processauthors_removeparen("This (foo) string (bar) contains (baz) parenthesis")
    'This  string  contains  parenthesis'
    """
    opening = 0
    dest = ''
    for char in authors_string:
        if char == '(':
            opening += 1
        elif char == ')' and opening > 0:
            opening -= 1
        elif opening == 0:
            dest += char
    return dest
