Amazon
| № п/п | Страна магазина / Country | Название произведения / Title | Формат произведения / Format |
| 1 | United States | Methods of concentration | eBook (kindle) |
| 2 | United Kingdom | Methods of concentration | eBook (kindle) |
| 3 | Germany | Methods of concentration | eBook (kindle) |
| 4 | France | Methods of concentration | eBook (kindle) |
| 5 | Spain | Methods of concentration | eBook (kindle) |
| 6 | Italy | Methods of concentration | eBook (kindle) |