F Fo F Fo F Fo F Fo S P Q a L 3 L 2 L 1 O 3 O 2 O 1 B A L 3 L 2 L 1 O 3 O 2 O 1 ( HV.1) m’ m k (HV.2) M N C A B R L M C A B R L A B D C A 2 F  1 F  3 F  t 2 t 1 P PV V O 2 H 2 V 1 V 2 t 0 C -273 0 p 0 P T P V P V P 0 V 1 V 2 V 1 2 V 1 2 A 0 V 1 V 2 P 1 P 2