A recommendation letter or letter of recommendation, also known as a letter of reference, reference letter or simply reference, is a document in which the writer assesses the qualities, characteristics, and capabilities of the person being recommended in terms of that individual's ability to perform a particular task or function.
This article is about stable isotope ratios. For the general category of stable nuclides, see Stable nuclide. The term stable isotope has a similar meaning to stable nuclide, but is preferably used when speaking of nuclides of a specific element.his article is about stable isotope ratios. For the general category of stable nuclides, see Stable nuclide. The term stable isotope has a similar meaning to stable nuclide, but is preferably used when speaking of nuclides of a specific element.
The Atomic number of Carbon is 6. The Atomic mass of Carbon depends on the isotope and may be from 8 to 22. Carbon 12 and Carbon 13 are the only stable isotopes of Carbon. Car â¦ bon 14 is the longest-lived unstable (radioactive) isotope. Only Carbon 12, 13 and 14 are found in nature.