english: In 2008, I picked up a scientific study looking at how many years we have of valuable materials to extract from the ground: copper, 61; tin, zinc, 40; silver, 29.
non_english: 2008. sam naišla na naučni rad koji proučava koliko još godina imamo na raspolaganju za vađenje  sirovina iz zemlje: bakar, 61; kalaj, cink, 40; srebro 29.