36

2 3 (1^st term)

$\langle V{P}^{2}V{P}^{2}V\rangle \Delta E_1\Delta E_2$

37

2 3 (2^nd term)

$-\langle V{P}^{2}V{P}^{3}V\rangle {\left(\Delta E_1\right)}^3$

38

1 1 1 2

$-\langle VPVPVPV{P}^{3}V\rangle \Delta E_1$

39

2 1 2

$\langle V{P}^{2}VPV{P}^{2}V\rangle {\left(\Delta E_1\right)}^2$

40

3 2 (1^st term)

$\langle V{P}^{2}V{P}^{2}V\rangle \Delta E_2\Delta E_1$

41

3 2 (2^nd term)

$-\langle V{P}^{3}V{P}^{2}V\rangle {\left(\Delta E_1\right)}^3$

42

1 2 2

$\langle VPV{P}^{2}V{P}^{2}V\rangle {\left(\Delta E_1\right)}^2$