You should be careful where you get those glasses for viewing the total eclipse next month. NASA is putting the word out about unsafe paper solar glasses being distributed and offering tips on how to confirm you have the real thing to protect your eyes.

For starters, your glasses should bear the logo of ISO, the international organization of standardization. They should also bear the ISO reference 12312-2. NASA also notes in its warning that you should be able to see the name of the manufacturer.

If the lenses are wrinkled or have scratches they are not safe for viewing the eclipse. If the glasses are older than three years, they are not recommended.