“PROOF WITHOUT WORDS: $\frac{a}{b}=\frac{c}{d} \Rightarrow \frac{a}{b}=\frac{c}{d}=\frac{a \pm c}{b \pm d}$ IN THE RANGE OF NATURAL NUMBERS”, FEJME, vol. 22, pp. 29–32, Jun. 2022, doi: 10.17654/0973563122006.