Specific health documents required for individual countries are listed under CUSTOMS REGULATIONS in each chapter of this book. The general requirements are: for re-entry to the United States and for entry to most foreign countries you need a smallpox vaccination certificate. It's advisable to have this before you leave the U. S. Yellow fever and cholera certificates are required by most countries from passengers who have come from an infected area. Nearly all countries of the world have adopted the international sanitary regulations of the World Health Organization.

These regulations establish the following periods of validity for vaccination certificates: smallpox-not less than 8 days nor more than 3 years old; yellow fever-not less than 10 days nor more than 6 years old; cholera-not less than 6 days nor more than 6 months old; typhus and typhoid-paratyphoid inoculation certificates are not required under the WHO sanitary regulations as a prerequisite for admission. They are recommended, however, for visits to some countries. The record of these inoculations must be entered by the health authority in the official WHO certificate of vaccination form. Passengers should obtain a copy of the form from the Pan American Ticket Office before obtaining their inoculations.

Tours-or pre-arranged travel plans-are often the answer to seeing the most and doing the most. Escorted tours are scheduled frequently; independent tours start any day you wish. All reservations are assured, you know the exact cost in advance, transportation is by the most direct and advisable routes with no timetable problems, hotels are carefully selected, meeting and transfer service and advice of a local representative are always available, and well-planned sightseeing leaves plenty of free time for personal activities. Often these established travel plans can be modified or extended to suit special interests and desires. You will find a wide choice of tours available.

In writing abroad from the United States, it's best to use International Air Mail. Rates per half-ounce are 10 cents to the Caribbean, Central and South America; 15 cents to Europe; 25 cents elsewhere. Air mail single postcards are 10 cents each to most countries, except Canada and Mexico, where they are 4 cents.

If you feel you can organize a group of friends or members of an organization for a trip abroad, check on Pan Am's Tour Conductor Plan, by which you can obtain your own passage free of charge.