One of the most important standards that the API has set is the method used for measuring the density of petroleum. This standard is called the API gravity. Specific gravity is a ratio of the density of one substance to the density of a reference substance, usually water.
The most common symptoms of RSI include: 1  Pain. 2  Tingling. 3  A feeling of restlessness in the joint. 4  Weakness. 5  Throbbing. 6  Stiffness or cramp.
Review the available symptom checkers for these symptoms of Common Variable Immunodeficiency: 1  Pneumonia -- Symptom Checker. 2  Swollen knee -- Symptom Checker. 3  Swollen ankle -- Symptom Checker.  Swollen wrist -- Symptom 1  Checker. Digestive symptoms -- Symptom Checker.  Enlarged spleen -- Symptom 1  Checker. Swollen glands -- Symptom Checker.