Historians have often discussed the  three estates  of the Western world'nobility, church, and commons.
( Historians ( ( ( have often ) ( discussed ( ( the ( three estates ) ) ( of ( ( ( the ( Western ( world ( ` ( nobility ( , ( church , ) ) ) ) ) ) ) and ) commons ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Historians)) (VP (VBP have) (ADVP (RB often)) (VP (VBN discussed) (NP (NP (DT the) (CD three) (NNS estates)) (PP (IN of) (NP (NP (DT the) (JJ Western) (NN world) (`` `) (NN nobility) (, ,) (NN church) (, ,)) (CC and) (NP (NNS commons))))))) (. .)))
Historians make comments on nobility, church and commons, the three estates of the Western world.
( Historians ( ( make ( ( ( comments ( on ( nobility ( , ( ( church and ) commons ) ) ) ) ) , ) ( ( the ( three estates ) ) ( of ( the ( Western world ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Historians)) (VP (VBP make) (NP (NP (NP (NNS comments)) (PP (IN on) (NP (NN nobility) (, ,) (NN church) (CC and) (NNS commons)))) (, ,) (NP (NP (DT the) (CD three) (NNS estates)) (PP (IN of) (NP (DT the) (JJ Western) (NN world)))))) (. .)))