The company said Mr. Ryan had resigned over differences in management strategy.
He however resigned in November 1982 over differences with Rawlings.
But he was forced to resign before Ayatollah Khomeini's death in 1989 over differences between the men.
However, he resigned in 1941 over differences.
But news reports suggested Gration did not resign over "differences" with Washington.
She resigned from the group on Monday over differences on the pace and type of efforts to help track down the child, she said.
He resigned the post on November 3, 1982 over differences which he could not compromise.
This institution offered courses and seminars for blue-collar workers, but he resigned in 1923 over differences with the trade union representatives.
A controversial, headstrong personality, he has often forced his chief ministers to resign over minor differences.
He resigned over differences with his colleagues about government ministers' access to the parliament.