Index: iknow-api/Models/SemesterSubjects.cs
===================================================================
--- iknow-api/Models/SemesterSubjects.cs	(revision 39f76a913d87c2aaad3ab3e11cb09f9857de636e)
+++ iknow-api/Models/SemesterSubjects.cs	(revision 1b20b226a74790f84dc06dc488f4f761b510a3f2)
@@ -1,17 +1,18 @@
 namespace iknow_api.Models
 {
+    // The student is reached through EnrolledSemester.UserId; the ER model
+    // links SemestersSubjects to Users only through the professor.
     public class SemesterSubject
     {
-        public int Id { get; set; } 
-        
-        public int UserId { get; set; }                 
+        public int Id { get; set; }
+
         public int EnrolledSemesterId { get; set; }
         public int SubjectId { get; set; }
         public int ProfessorId { get; set; }
         public bool Signature { get; set; }
-        public User? User { get; set; }                 
+
         public EnrolledSemesters? EnrolledSemester { get; set; }
         public Subject? Subject { get; set; }
-        public User? Professor { get; set; }           
+        public User? Professor { get; set; }
         public PassedSubject? PassedSubject { get; set; }
     }