If the towel soaks through, use a fresh one to mop up the rest. Careful dabbing will minimize the size of the stain by not spreading the liquid around. Press lightly up and down with care so as to not damage the paper. Be absolutely sure your work area is clean or you will have a second stain to remove! Hold the paper down at two or more corners with clean, waterproof objects. This step is to minimize the possibility of wrinkling the page. Repeat this with fresh paper towels until you stop seeing color come off onto the towel.  With water based stains that haven’t been left to dry, most pigment will be removed using just this method. If your stain persists, move on to the next step. In a bowl, mix a half cup of  white vinegar with half a cup of water. Most other types of vinegar will themselves stain paper, so be sure the vinegar you use is completely clear. This step should be done away from the paper to avoid spills and further damage. Check to see if any ink has come off onto the cotton ball. Some printing methods produce ink that will not run, but others will. In case it does, be sure to select the smallest, least conspicuous part of the paper to test.  If ink has come off of the document, further attempts at removing the stain may ruin your paper.  If the cotton ball is clear, proceed to the next step. Any remaining pigment should be dissolved by the vinegar and be lifted from the page. If the stain was large or dark, you may have to repeat this step with a fresh soaked cotton ball as the first becomes dirty. Using fresh cotton balls ensures you don't inadvertently spread the stain across the page. Allow the paper to air dry. If the item you just cleaned was the page of a book, leave the book open to that page. Use weights to hold down paper towels on the pages on either side of the freshly cleaned page.

===
Write a summary of the previous text in Vietnamese:
Thấm chất lỏng được chừng nào hay chừng ấy bằng tờ khăn giấy khô gập lại. Lau một mặt phẳng không thấm nước sao cho thật sạch và khô, sau đó trải trang giấy lên. Thấm ướt một tờ khăn giấy sạch và cẩn thận chấm lên vết bẩn lần nữa. Chuẩn bị dung dịch giấm pha loãng. Tẩm dung dịch giấm vào bông gòn và cẩn thận chấm lên một chữ nhỏ trong tài liệu. Chấm bông gòn lên vết bẩn. Dùng khăn giấy khô thấm lên chỗ vết bẩn đã được làm sạch và hong khô giấy.