International economics is the study of how the production of one nation is purchased by another nation and how the currency of one nation is exchanged for the currency of another nation to pay for this production. What exactly international economics is and what it covers tend to depend on the views of the person using the definition. Most journals are highly specialized, although some of the oldest journals publish articles and scientific papers across a wide range of scientific fields. Scientific journals contain articles that are peer reviewed, to ensure that articles meet the journal's standards of quality, and scientific validity. The publication of the results of research is an essential part of the scientific method. If they are describing experiments or calculations, they must supply enough details that an independent researcher could repeat the experiment or calculation to verify the results. Each such journal article becomes part of the permanent scientific record.