NL-NWO 1968 Problem 3

$\vartriangle ABC \sim \vartriangle A'B'C'$ . $\vartriangle ABC$ has sides $a,b,c$ and $\vartriangle A'B'C'$ has sides $a',b',c'$ . Two sides of $\vartriangle ABC$ are equal to sides of $\vartriangle A'B'C'$ . Furthermore, $a < a'$ , $a < b < c$ , $a = 8$ . Prove that there is exactly one pair of such triangles with all sides integers.