[{"sf": "ETA", "lfs": [{"lf": "endothelin-A", "freq": 111, "since": 1992, "vars": [{"lf": "endothelin-A", "freq": 49, "since": 1993}, {"lf": "endothelin A", "freq": 46, "since": 1993}, {"lf": "endothelinA", "freq": 8, "since": 1992}, {"lf": "Endothelin A", "freq": 6, "since": 1995}, {"lf": "Endothelin-A", "freq": 1, "since": 2004}, {"lf": "endothelin a", "freq": 1, "since": 2006}]}, {"lf": "exotoxin A", "freq": 79, "since": 1984, "vars": [{"lf": "exotoxin A", "freq": 73, "since": 1984}, {"lf": "Exotoxin A", "freq": 6, "since": 1988}]}, {"lf": "A receptor", "freq": 47, "since": 1993, "vars": [{"lf": "A receptor", "freq": 17, "since": 1993}, {"lf": "endothelin receptor A", "freq": 9, "since": 1994}, {"lf": "endothelin receptor subtype A", "freq": 8, "since": 1994}, {"lf": "receptor type A", "freq": 5, "since": 2000}, {"lf": "endothelin receptors A", "freq": 2, "since": 2005}, {"lf": "A receptors", "freq": 2, "since": 1995}, {"lf": "receptor, type A", "freq": 1, "since": 2002}, {"lf": "receptors type A", "freq": 1, "since": 2002}, {"lf": "receptor type-A", "freq": 1, "since": 2005}, {"lf": "endothelin receptor subtype-A", "freq": 1, "since": 1995}]}, {"lf": "endothelin type A", "freq": 34, "since": 1993, "vars": [{"lf": "endothelin type A", "freq": 17, "since": 1994}, {"lf": "ET type A", "freq": 7, "since": 1999}, {"lf": "endothelin subtype A", "freq": 6, "since": 1993}, {"lf": "ET) type A", "freq": 1, "since": 1993}, {"lf": "endothelin type-A", "freq": 1, "since": 2000}, {"lf": "endothelin subtype-A", "freq": 1, "since": 2008}, {"lf": "ET type-A", "freq": 1, "since": 2000}]}, {"lf": "exfoliative toxin A", "freq": 21, "since": 1987, "vars": [{"lf": "exfoliative toxin A", "freq": 16, "since": 1987}, {"lf": "Exfoliative toxin A", "freq": 4, "since": 1997}, {"lf": "exfoliative toxins A", "freq": 1, "since": 1991}]}, {"lf": "5,8,11,14-eicosatetraynoic acid", "freq": 16, "since": 1975, "vars": [{"lf": "5,8,11,14-eicosatetraynoic acid", "freq": 7, "since": 1975}, {"lf": "eicosa-5,8,11,14-tetraynoic acid", "freq": 4, "since": 1975}, {"lf": "5,8,11,14-eicosatetraenoic acid", "freq": 3, "since": 1978}, {"lf": "5,8,11,14-Eicosatetraynoic acid", "freq": 1, "since": 1976}, {"lf": "eicosa-5,8,11, 14-tetraynoic acid", "freq": 1, "since": 1975}]}, {"lf": "European Thyroid Association", "freq": 15, "since": 1987, "vars": [{"lf": "European Thyroid Association", "freq": 15, "since": 1987}]}, {"lf": "etanidazole", "freq": 12, "since": 1990, "vars": [{"lf": "etanidazole", "freq": 10, "since": 1990}, {"lf": "Etanidazole", "freq": 2, "since": 1995}]}, {"lf": "ethionamide", "freq": 12, "since": 1966, "vars": [{"lf": "ethionamide", "freq": 9, "since": 1966}, {"lf": "Ethionamide", "freq": 2, "since": 2000}, {"lf": "ethionamid", "freq": 1, "since": 1970}]}, {"lf": "erythrogenic toxin A", "freq": 11, "since": 1986, "vars": [{"lf": "erythrogenic toxin A", "freq": 6, "since": 1986}, {"lf": "Erythrogenic toxin type A", "freq": 2, "since": 1993}, {"lf": "erythrogenic toxin type A", "freq": 2, "since": 1992}, {"lf": "erythrogenic toxins type A", "freq": 1, "since": 1996}]}, {"lf": "endotracheal aspirate", "freq": 9, "since": 1993, "vars": [{"lf": "endotracheal aspirate", "freq": 4, "since": 1993}, {"lf": "endotracheal aspiration", "freq": 2, "since": 2004}, {"lf": "endotracheal aspirates", "freq": 2, "since": 2003}, {"lf": "Endotracheal aspirates", "freq": 1, "since": 2001}]}, {"lf": "etanercept", "freq": 9, "since": 2001, "vars": [{"lf": "etanercept", "freq": 8, "since": 2001}, {"lf": "Etanercept", "freq": 1, "since": 2008}]}, {"lf": "ethacrynic acid", "freq": 8, "since": 1979, "vars": [{"lf": "ethacrynic acid", "freq": 7, "since": 1979}, {"lf": "Ethacrynic acid", "freq": 1, "since": 1996}]}, {"lf": "extended topochemical atom", "freq": 8, "since": 2004, "vars": [{"lf": "extended topochemical atom", "freq": 8, "since": 2004}]}, {"lf": "asymmetry parameter", "freq": 7, "since": 1983, "vars": [{"lf": "asymmetry parameter", "freq": 4, "since": 1992}, {"lf": "asymmetry parameters", "freq": 2, "since": 2000}, {"lf": "Asymmetry parameter", "freq": 1, "since": 1983}]}, {"lf": "resistance (R), elastance (E), and hysteresivity", "freq": 6, "since": 1992, "vars": [{"lf": "resistance (R), elastance (E), and hysteresivity", "freq": 5, "since": 1992}, {"lf": "Resistance (R), elastance (E) and hysteresivity", "freq": 1, "since": 2004}]}, {"lf": "extrathoracic airway", "freq": 6, "since": 1979, "vars": [{"lf": "Extrathoracic airway", "freq": 3, "since": 1987}, {"lf": "extrathoracic airway", "freq": 3, "since": 1979}]}, {"lf": "solar energy-to-electricity conversion efficiency", "freq": 5, "since": 2003, "vars": [{"lf": "solar energy-to-electricity conversion efficiency", "freq": 3, "since": 2003}, {"lf": "solar energy-to-electricity conversion efficiencies", "freq": 1, "since": 2005}, {"lf": "solar energy to electricity conversion efficiencies", "freq": 1, "since": 2007}]}, {"lf": "eicosatrienoic acid", "freq": 5, "since": 1982, "vars": [{"lf": "eicosatrienoic acid", "freq": 5, "since": 1982}]}, {"lf": "electrothermal atomization", "freq": 3, "since": 1981, "vars": [{"lf": "electrothermal atomization", "freq": 2, "since": 1981}, {"lf": "electrothermal atomizer", "freq": 1, "since": 1990}]}, {"lf": "Emanation thermal analysis", "freq": 3, "since": 2002, "vars": [{"lf": "Emanation thermal analysis", "freq": 2, "since": 2002}, {"lf": "emanation thermal analysis", "freq": 1, "since": 2005}]}, {"lf": "estimated transmitting abilities", "freq": 3, "since": 1997, "vars": [{"lf": "estimated transmitting abilities", "freq": 3, "since": 1997}]}, {"lf": "The Employment and Training Administration", "freq": 3, "since": 1991, "vars": [{"lf": "The Employment and Training Administration", "freq": 3, "since": 1991}]}]}]