31.   The strength of the book lies in the fact that the material is from classroom experience.

32.   There is a labor force with all the necessary skills, and there are materials.

33.   There is evidence that volatile materials have always been scarce on the Moon.

34.   There is likely to be material that is at variance with your own views.

35.   There is material before it and emotional charge after it which make it unwieldy.

36.   These materials are too fine to have a practical purpose in daily life.

37.   This material is at serious risk of being stolen.

38.   This stony material is certainly much easier to crush and handle than a massive chunk of stainless steel.