“PROOF WITHOUT WORDS: $a, b, c, d>0$; $ \frac{a}{b}=\frac{c}{d} \Rightarrow \frac{a}{b}=\frac{c}{d}=\frac{s a+t c}{s b+t d} $”, FEJME, vol. 26, no. 2, pp. 71–77, Aug. 2024, doi: 10.17654/0973563124008.