on a stamp one year after their demise. The choice of postage stamp color may be specified, acting as a sort of color code to different rates. Most countries issue commemorative issues from time to time, perhaps to celebrate some special event, with designs relating to the event. While they are legitimate postage stamps, and often used for routine post, they are intended to appeal particularly to stamp collectors. Stamps that are collected without being used are paid for, but the purchaser chooses not to use the postal service purchased, leaving 100% clear profit. First day covers, often containing more stamps than are required for postage, are an additional source of revenue. This source of money is not inexhaustible, as excessive stamp issues go unpurchased. Some countries, usually poorer ones, produce many special issues intended purely for collectors from other countries. These stamps are designed for visual appeal, with attractive brightly coloured designs on interesting topics, often large and of unusual shape. Themes have included space-related subjects from a country with no space program, polar animals from a country on the equator, Western rock stars from a conservative Muslim country, and so forth. International organizations of philatelists discourage the practice, not wanting collectors to be discouraged by floods of stamps which will never have any rarity value. See stamp program for more detail. Textual elements Nearly all stamps have some amount of text embedded in their design. In addition to the expected denomination and country name, textual elements may include a statement of purpose ("postage", "official mail", etc.), a plate number, the name of a person being portrayed, the occasion being commemorated, the year of stamp issue, and national mottoes. Occasionally designs use text as their primary design element; for instance, a series of US stamps from the 1970s featured quotations from the United States Declaration of Independence. In general however, text has come to be used more sparingly in recent years. Countries with multiple languages and multiple scripts may need to write the material multiple times. Labuan is an early example; more recently, stamps of Israel include its name in Hebrew, Latin, and Arabic characters. In addition to text woven into the description, stamps may also have inscriptions in the outside margin. These are almost always at the bottom, and are usually the name of the printer and/or designer. Occasionally a textual description of the design is found in