TITLE: Whitney sum formula for Pontryagin classes II
QUESTION [6 upvotes]: I have read in several places that the total Pontryagin classes of real vector bundles satisfy a Whitney sum formula $p(E\oplus F) = p(E)\cdot p(F)$ modulo 2-torsion. I would like to understand the 2-torsion part better.

Is there a reference which describes the difference between $p(E\oplus F)$ and $p(E)\cdot p(F)$, perhaps in terms of Bocksteins of Stiefel-Whitney classes of $E$ and $F$?

This question was previously part of Whitney sum formula for Pontryagin classes I; Qiaochu Yuan's answer to that question might be helpful.

REPLY [9 votes]: Brown, Edgar H., Jr.
The cohomology of BSOn and BOn with integer coefficients. 
Proc. Amer. Math. Soc. 85 (1982), no. 2, 283–288. 
Theorem 1.6, last sentence:
Under Whitney sum,
$p_q\mapsto  \sum_j r_{2q-j}\otimes r_j$, where
$r_{2s} = p_s$ and $r_{2s+1} = (\delta w_{2s})^2+ p_s\delta w_1$.