can evaluate Eq. (\[23112013a\]) at $r_0$ to obtain $$Form_1(r_0)=\frac{S}{r_0^2}[1-(1+S)/2]\lim_{r\to r_0}(1-r_0/r)^{S-2}=\Biggl\{ \begin{array}{lr} 0 & S>2,\\ \textrm{finite}\neq 0 & S=2,\\ \infty & 1<S<2. \end{array} \label{23112013e}$$ The remaining expressions take the form $$Form_2=-\frac{W_m^2}{W}\frac{\Phi'}{R}=-\frac{r_0SW_m}{2r^3}W^{S-2}, \label{23112013f}$$ $$Form_3=-\frac{Sr_0}{2r^3}\left[1-\frac{(1+S)}{2S}\frac{r_0}{r} \right]W^{S-2}, \label{23112013h}$$ $$Form_4=\frac{W-W_m^2}{r^2}W^{S-2},\label{23112013j}$$ where we are using $W_m=1-r_m/r$. It is straightforward to check that the “forms” (\[23112013f\])-(\[23112013j\]) yield the same qualitative result as that of Eq. (\[23112013e\]). Therefore, the region $A$ becomes flat far from the throat only for $S>2$. Here, we call the attention to the fact that the region $A$ may be bounded, i.e., the time to go from $r_m$ to $r_0$ from the viewpoint of the traveler may be finite. If the point $r_0$ is not a physical singularity, then one will have to maximally extend Wyman’s manifold to see what happens below $r_0$.

Condition \[9082013a\]
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The two-surface characterized by a fixed moment of time and $\theta=\pi/2$ cannot be completely embedded into a three-dimensional Euclidean space. We can see that in the following way. From Eq. (27) in Ref. [@citeulike:5196630], we have $$\frac{dz}{dR}=\pm \left(R/b-1 \right)^{-1/2}, \label{30012014c}$$ where $z$ is the “$z-$coordinate” of the cylindrical coordinate system. For $r<r_1$, the term $R/b-1$ is negative. Thus, the interval $(r_0,r_1]$ cannot be used in Eq. (\[30012014c\]). Nonetheless, 