"It is believed that the Chinese invented gunpowder" - THE CHINESE...
The Chinese are believed to have invented gunpowder.
"People think that neither side wanted war" - NEITHER SIDE IS...
Neither side is thought to have wanted war.
"Someone used a knife to open this window" - THIS WINDOW...
This window was opened with a knife.
"Apparently the ship did not sustain any damage" - THE SHIP...
The ship appears not to have sustained any damage.
"Nobody had invited Jean to the party, which annoyed her" - AS SHE...
As she had not been invited to the party, Jean was annoyed.
"We thought it was necessary to send a telegram" - IT...
It was thought necessary to send a telegram.
"The police believe that a professional thief stole the statue" BEEN
The statue is believed to have been stolen by a professional thief.
"The treasure is thought to date from the 13th century" - IT...
It is thought that the treasure dates from the 13th century.
"People say that Mrs. Turner was having business difficulties" BEEN
Mrs. Turner is said to have been having business difficulties.
"Everyone thought the painting had been destroyed" - THE PAINTING...
The painting was thought to have been destroyed.
"There is confirmation of Mr. Jackson's resignation" - IT...
It is /has been confirmed that Mr. Jackson has resigned