at the end of both articles were lists of works , which showed that stravinsky and diaghilev had collaborated on the following ballets : the firebird , 1910 petrushka , 1911 the rite of spring , 1913 pulcinella , 1920 les noces , 1923 helstof looked at the others and said , nothing from the time period of stravinskys letter that we have here , 1914 .