Task: Text to Code
Input (English): Step 1: For each row in course table, find the corresponding rows in section table.
Step 2: find title of the results of step 1 whose semester equals Differential Geometry
Output (English): SELECT T1.title FROM course AS T1 JOIN section AS T2 ON T1.course_id = T2.course_id WHERE T2.semester = "Differential Geometry"