Olivera et al (1992)
AO1

Birch et al (1990)
AO1

:) Brown & Ogden (1994)
AO2

:) Lowe et al (1998)
AO2

:( However...
AO2

Westcombe & Wardle (1997)
AO1

Liou (2001)
AO1

:) Rapoport (2003)
AO2

:( However/Steptoe et al (1995)
AO2