Joints are mainly classified structurally and functionally. Other elements are occasionally classified as metalloids. These are also formally classified as "stable". Natural resources may be further classified in different ways. These can be classified and recorded in several forms. Catalysis is so pervasive that subareas are not readily classified. However, plasmids, like viruses, are not generally classified as life. Sexual offenders are sometimes classified by level. IL-6 had previously been classified as a proinflammatory cytokine. The Kassite language has not been classified. Nigerian legislation may be classified as follows. This wolf has not been taxonomically classified. "Leptospira" are also classified based on their serovar. Tomatoes are also classified as determinate or indeterminate. Uruguay was initially classified as being uncooperative.