###HUMAN: When can I take 421 ?, ###ASSISTANT: SELECT DISTINCT semester.semester, semester.year FROM course, course_offering, semester WHERE course.course_id = course_offering.course_id AND course.department = 'EECS' AND course.number = 421 AND course_offering.semester = semester.semester_id AND semester.semester_id > (SELECT SEMESTERalias1.semester_id FROM semester AS SEMESTERalias1 WHERE SEMESTERalias1.semester = 'WN' AND SEMESTERalias1.year = 2016) ORDER BY semester.semester_id LIMIT 1