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 8.5x11 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.