Heisenberg

Proper noun

  had

Auxiliary

  been

Auxiliary

  studying

Verb

  the

Determiner

  papers

Noun

  of

Adposition

  Paul

Proper noun

  Dirac

Proper noun

  and

Coordinating conjunction

  Pascual

Proper noun

  Jordan

Proper noun

.

Heisenberg had been studying the papers of Paul Dirac and Pascual Jordan.

Heisenberg had been studying the papers of Paul Dirac and Pascual Jordan.