These are words such as that (thing), everyone and none that I take for granted in English but find difficult to memorize in Esperanto, even though they are arrayed in a perfectly logical way.
To make your own flash cards, download both of the attached files. Print the five pages on 8.5×11 inch thin card or thick paper. Use the other file to print the other side, using your printer’s instructions. Use the printed guidelines to cut the cards apart; each will be the size of a US business card.
Now, how I made these PDFs is another matter, and the subject of a future blog post.