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4. We also take this opportunity to correct some errors in eqs. (10), (11) and (12) of ref. (2) (10) and (11) should read respectively as $$\begin{gathered} \Phi ^1 \left( {\left[ \theta \right],\left[ \chi \right];0,{\text{ t}}_{\text{2}} |E_0 } \right) = 1, \hfill \\ \Phi ^2 \left( {\left[ \theta \right],\left[ \chi \right];0,{\text{ t}}_{\text{2}} |E_0 } \right) = 2,\int {R^2 \left( {E^1 |E_0 } \right)\left[ {\exp \left[ {i\theta \left( {E^1 } \right)\chi \left( {E_2 } \right)} \right]\pi \left( {E_2 |E^1 ;t_2 } \right)} \right]dE^1 dE_2 ,} \hfill \\ \Phi ^\iota \left( {\left[ \theta \right],\left[ \chi \right];0,{\text{ t}}_{\text{2}} |E_0 } \right) = 1 \left( {i = 1,2} \right), \hfill \\ \end{gathered} $$ , where π(E 2|E′; t) dE 2 denotes the probability that an electron of energy E′ at t = 0 drops to an energy between E 2 and E 2 + dE 2 at t. The left-hand side of (12) should be corrected to read as E {dM(E 1, t 1; E 2, t 2)} while in eq. (8) the integration under the exponential sign is over the variables x 1, x 2 and t 1 (treated as dummy).
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