Authors often try to justify their statements by suggesting they have acquired the information from an authoritative source. If you wish to refer to a source, however, do not do so vaguely as in the following example. A straightforward statement is preferable to a vague attribution. Therefore, not
| Student registrations have been observed to be increasing in some subjects that were previously determined to be unfashionable. |
but
| Student registrations have been increasing in some previously unfashionable subjects. |
and not
| It has been shown that visiting lecturers have been using this new resource. |
but
| Visiting lecturers have been using this new resource. |