Other papers

Du Xinxing, 1997

Madhava Rao and Kaila, 1986

Liritzis and Tsapanos, 1992

Periodicities

7; 14; 22 and 42 years.

3 to 12 years.

3; 4.5; 6.5; 8; 9; 14 - 20

and 31 - 34 years.