An important milestone in Respighi's career took place when Arturo Toscanini asked the composer to have one of his compositions performed in a series of twelve concerts in Milan in February 1918. Respighi reluctantly picked "Fountains of Rome", which had thus far only been performed at its 1917 premiere. The concert was a huge success and placed Respighi as one of the leading Italian composers of the early 20th century, prompting the start of a longterm, though sometimes tumultuous, relationship with Toscanini. Two months after the concert, Respighi allowed Casa Ricordi to publish the score of the tone poem in a deal that granted the composer 40% of the rental and performance rights of the work. Respighi succumbed to illness soon after with a mild case of Spanish flu. By the summer of 1918, Respighi had entered negotiations to translate and publish Italian versions of "Theory of Harmony" (1922) by composer Arnold Schoenberg and a book on musical counterpoint by Sergei Taneyev, but these never materialised.