Speech Delay

Dear All,

My son was diagnosed on autistic spectrum last year. He is 5 now and started main stream school this year.

The main area of concern for me is his speech delay. He hardly say one words and  is all by himself. As he do not speak thus stay aloof from kids of his age. At home, If he needs anything he will just pin point or may be use one word. 

Is there any good/trusted  book online which I can buy and will be useful in helping him frame sentences,