"1989"^^ . . "J.P. den Hartog" . "Hartog, J.P. den (1901-1989)" . . "Den Hartog, Jacob Pieter" . _:Be9f204ba993015b938c598ca17a92444 . . "den Hartog" . . "1901"^^ . "mechanisch ingenieur"@nl . "Hartog, Jacob Pieter den" . "J.P." . _:Be9f204ba993015b938c598ca17a92444 . _:Be9f204ba993015b938c598ca17a92444 . _:Be9f204ba993015b938c598ca17a92444 "2023-05-22"^^ . _:Be9f204ba993015b938c598ca17a92444 . _:Be9f204ba993015b938c598ca17a92444 . _:Be9f204ba993015b938c598ca17a92444 "072280921" . _:Be9f204ba993015b938c598ca17a92444 . _:Be9f204ba993015b938c598ca17a92444 . _:Be9f204ba993015b938c598ca17a92444 .