def form_get_request_to_list_songs_of_playlist(playlist_id, api_key, page_token='', max_results='50'):
    """
	Form get request to list all playlist items of a certain playlist.
	"""
    get_request = 'https://www.googleapis.com/youtube/v3/playlistItems/?maxResults={}&playlistId={}&part=snippet%2CcontentDetails&key={}'.format(
        max_results, playlist_id, api_key)

    if page_token:
        get_request += '&pageToken={}'.format(page_token)

    return get_request