diff --git a/models/Section.js b/models/Section.js
index 24ba368c51f541473d8c9ca5f894ff430965ffe6..5552e2488d98ecb15ba50bbc5aefc019e011d41c 100644
--- a/models/Section.js
+++ b/models/Section.js
@@ -3,7 +3,16 @@ module.exports = function (sequelize, DataTypes) {
         // unique index/key
     crn: {
       type: DataTypes.STRING,
-      unique: true
+      unique: true,
+      primaryKey: true
+    },
+
+    semester: {
+      type: DataTypes.STRING,
+      references: {
+        model: 'Semester',
+        key  : 'slug'
+      }
     },
 
     name: DataTypes.STRING,
diff --git a/models/Semester.js b/models/Semester.js
index d98f9e4433be2fbb15d04e76fcf384817dbf9482..27f2c6652a05bb0f1bd825436bc3daee44a4e4d4 100644
--- a/models/Semester.js
+++ b/models/Semester.js
@@ -2,7 +2,16 @@ module.exports = function (sequelize, DataTypes) {
   var Semester = sequelize.define('Semester', {
     slug: {
       type: DataTypes.STRING,
-      unique: true
+      unique: true,
+      primaryKey: true
+    },
+
+    university: {
+      type: DataTypes.STRING,
+      references: {
+        model: 'University',
+        key  : 'slug'
+      }
     },
 
     name: DataTypes.STRING
diff --git a/models/University.js b/models/University.js
index a975a76523984ec205e4ed189d4b0560be117498..e9a2e23ac733c8c328069f6bd8053bd5df5b044c 100644
--- a/models/University.js
+++ b/models/University.js
@@ -3,7 +3,8 @@ module.exports = function (sequelize, DataTypes) {
     slug: {
       type: DataTypes.STRING,
       allowNull: false,
-      unique: true
+      unique: true,
+      primaryKey: true
     },
 
     name: {