11.   Another useful guide to seeing, in this case every North American bird, by the son of the ornithologist Fred Sibley.

12.   Another useful general guide is the personal-finance section of the Whole Internet Catalog, which offers a range of topics but does not rate sites.

13.   Anthony Gottlieb finds that archaeologists are the most useful guides to consciousness.

14.   As useful guides -- well, perhaps.

15.   But as President Clinton considers his future military options, and comes under ever greater pressure to unseat Saddam, he may find the gulf war a useful guide.

16.   But the documents do set forth the political philosophy of a party and as such can be a useful guide to the direction a newly elected president might take.

17.   History, a usually useful guide, does tell us that Septembers are not typically stellar months for stocks.

18.   Justice Anthony M. Kennedy suggested that unrestrained speech by judicial candidates could be a useful guide for voters.

19.   LEWES CHAMBER OF COMMERCE will send useful guides, with maps and walking tours.

20.   Mayo departs somewhat from the topic of medicines to provide a very useful guide to first aid.