1.   A basic example occurs in an electron beam - so important in television and radio.

2.   A convenient notes section on each page points out major features encountered and emphasises detail occurring in the plate illustrated.

3.   A few related species occur in the Jurassic.

4.   A noticeable change in the nature of protest has occurred in recent years.

5.   Abscesses form classically under the lower jaw but can occur in other sites.

6.   All this occurs in magnetic fields very much above the maximum tolerated by the superconducting state.