( ( For years ) ( ( ( the processes ) ( of ( ( ( formation and ) decay ) ( of ( the ( long-lived ( nuclear isomers ) ) ) ) ) ) ) ( ( were ( studied ( by ( ( A.V.Davydov et ) al. ) ) ) ) . ) ) )
(ROOT (S (PP (IN For) (NP (NNS years))) (NP (NP (DT the) (NNS processes)) (PP (IN of) (NP (NP (NN formation) (CC and) (NN decay)) (PP (IN of) (NP (DT the) (JJ long-lived) (JJ nuclear) (NNS isomers)))))) (VP (VBD were) (VP (VBN studied) (PP (IN by) (NP (NNP A.V.Davydov) (CC et) (NNP al.))))) (. .)))
For years the processes of formation and decay of the long-lived nuclear isomers were studied by A.V.Davydov et al.
(ROOT (S (NP (DT The) (JJ long-lived) (NNS isotopes)) (VP (VBP require) (NP (NP (NNS thousands)) (PP (IN of) (NP (NP (NNS years)) (PP (TO to) (NP (NN decay)))))) (PP (TO to) (NP (NP (DT a) (JJ safe) (NN level)) (PP (IN in) (NP (DT a) (JJ nuclear) (NN reactor)))))) (. .)))