Asymptotic formula for Carmichael numbers with three prime factors

Let $C(x)$ denote the number of Carmichael numbers $n\leq x$ with exactly three prime factors. Three-factor Carmichael number conjecture. As $x\to\infty$, one has

$$C(x)\sim C\frac{x^{1/3}}{\log^3 x},$$

where $C$ is an absolute constant that can be given precisely. This asymptotic would provide the missing count for one of the two families attaining the maximal proportion of strong liars, but the source does not establish it or indicate that it has been resolved.