def find_litho_markers(tokens, regex):
    """Find lithology lithology terms that match a regular expression

    Args:
        tokens (iterable of str): the list of tokenised sentences.
        regex (regex): compiles regular expression  e.g. re.compile('sand|clay')

    Returns:
        (list of str): tokens found to be matching the expression
    """
    return list(filter(regex.search, tokens))
