1. I can't go with them as I am to be at the Institute at half past nine.
2. If you want to understand this phenomenon better, you have to look through some articles devoted to this problem.
3. As this question is not solved the meeting has to be put off.
4. At ten a.m. he is to make a report, I think it will be interesting to listen to him.
5. As he made many mistakes in his last work he has to rewrite it.