Let $f\colon Y\to X$ be a proper morphism between smooth quasiprojective $k$-algebraic varieties. Denote by $\psi^j$ the $j$-th Adams operation on the Grothendieck group of vector bundles and $\theta^j(T_f)$ the $j$-th cannibalistic class of the relative tangent bundle $T_f$. The Adams Riemann-Roch theorem states that for any $j$ the diagram $\require{AMScd}$ $$ \begin{CD} K_0(Y)@>f_*>>K_0(X)\\ @V\theta^j(T_f)\cdot \psi^jVV@VV\psi^jV\\ K_0(Y)\otimes\mathbb{Z}[\tfrac{1}{j}]@>f_*>>K_0(X) \otimes \mathbb{Z}[\tfrac{1}{j}] \end{CD} $$ commutes.

The oldest reference I know is Theorem 7.6 of Chapter V in W. Fulton; S. Lang: Riemann-Roch algebra. Grundlehren der Mathematischen Wissenschaften , 277. Springer-Verlag, New York, 1985. x+203 pp.. However, that reference is already very general (it does not even require schemes to be over a field) and 1985 is very "late" for such a Riemann-Roch type statement. Therefore my question:

$ \phantom{aaaaaaaa}$**What is the original reference for the Adams Riemann-Roch theorem?**

I am looking for something as Borel-Serre's paper is for Grothendieck-Riemann-Roch.