Apply 1/3 cleaning vinegar and 2/3 warm water with a small squeegee. Try to work out of the direct sun and keep the windshield wet for a while then dry with newspaper which acts like a fine abrasive. Avoid touching other areas as the ink may transfer but will leave glass with a polished look. The previous owner of my car managed to scratch the outside of the windshield with a gritty snowball!