Sentence:  Your <WSD>invitation</WSD> to write about Serge Prokofieff to honor his 70 th Anniversary for the April issue of Sovietskaya Muzyka is accepted with pleasure , because I admire the music of Prokofieff ; and with sober purpose , because the development of Prokofieff personifies , in many ways , the course of music in the Union of Soviet Socialist Republics . 
Meaning of the word marked with <WSD> tags:  a request (spoken or written) to participate or be present or take part in something