diff --git a/lib/kosapi_client/entity.rb b/lib/kosapi_client/entity.rb
index 34c7ff1..dde508f 100644
--- a/lib/kosapi_client/entity.rb
+++ b/lib/kosapi_client/entity.rb
@@ -7,6 +7,7 @@
 require 'kosapi_client/entity/data_mappings'
 require 'kosapi_client/entity/base_entity'
 require 'kosapi_client/entity/result_page'
+require 'kosapi_client/entity/coursin'
 require 'kosapi_client/entity/course_event'
 require 'kosapi_client/entity/course'
 require 'kosapi_client/entity/timetable_slot'
diff --git a/lib/kosapi_client/entity/coursin.rb b/lib/kosapi_client/entity/coursin.rb
new file mode 100644
index 0000000..f0855ac
--- /dev/null
+++ b/lib/kosapi_client/entity/coursin.rb
@@ -0,0 +1,17 @@
+module KOSapiClient
+  module Entity
+    class Coursin < BaseEntity
+
+      map_data :capacity
+      map_data :capacity_overfill, Integer
+      map_data :course # TODO: fix circular reference. map_data :course, Course
+      map_data :occupied, Integer
+      map_data :semester
+      map_data :tutorial_capacity, Integer
+      map_data :examiners, [Link], array_wrapper_element: :teacher
+      map_data :guarantors, [Link], array_wrapper_element: :teacher
+      map_data :instructors, [Link], array_wrapper_element: :teacher
+      map_data :lecturers, [Link], array_wrapper_element: :teacher
+    end
+  end
+end
diff --git a/lib/kosapi_client/entity/data_mappings.rb b/lib/kosapi_client/entity/data_mappings.rb
index e843466..81e1f46 100644
--- a/lib/kosapi_client/entity/data_mappings.rb
+++ b/lib/kosapi_client/entity/data_mappings.rb
@@ -66,12 +66,17 @@ def set_mapped_attributes(instance, source_hash)
         def set_mapped_attribute(instance, name, source_hash, mapping_options)
           namespace = mapping_options[:namespace]
           src_element = mapping_options[:element] || name
+
           if namespace
             key = "#{namespace}_#{src_element}".to_sym
           else
             key = src_element
           end
+
           value = source_hash[key]
+
+          value = value[mapping_options[:array_wrapper_element]] if mapping_options.key? :array_wrapper_element
+
           if value.nil?
             raise "Missing value for attribute #{name}" if mapping_options[:required]
             if mapping_options[:type].is_a?(Array)
diff --git a/lib/kosapi_client/request_builder.rb b/lib/kosapi_client/request_builder.rb
index 2fa046d..8446924 100644
--- a/lib/kosapi_client/request_builder.rb
+++ b/lib/kosapi_client/request_builder.rb
@@ -19,6 +19,11 @@ def limit(num)
       self
     end
 
+    def sem(code)
+      @url_builder.set_query_param(:sem, code)
+      self
+    end
+
     def query(params = {})
       raise 'Empty parameters to query are not allowed' if params.empty?
       if params.instance_of?(String)
diff --git a/lib/kosapi_client/resource/courses_builder.rb b/lib/kosapi_client/resource/courses_builder.rb
index 54854c5..faff6d0 100644
--- a/lib/kosapi_client/resource/courses_builder.rb
+++ b/lib/kosapi_client/resource/courses_builder.rb
@@ -7,6 +7,61 @@ def detail(level = 1)
         self
       end
 
+      ###
+      # GET /courses/{code}/parallels
+      #
+      # URI: https://kosapi.fit.cvut.cz/api/3/courses/{code}/parallels/
+      # @link: https://kosapi.fit.cvut.cz/projects/kosapi/wiki/Courses#GET-coursescodeparallels
+      ##
+      # Example:
+      #   client.courses.find({course_code}).parallels
+      #   client.courses.find({course_code}).sem({semester_code}).parallels
+      ###
+      def parallels
+        raise 'Call #find before asking for parallels' unless id_set?
+        url_builder.set_path(id, 'parallels')
+        self
+      end
+
+      ###
+      # GET /courses/{code}/students
+      #
+      # URI: https://kosapi.fit.cvut.cz/api/3/courses/{code}/students/
+      # @link: https://kosapi.fit.cvut.cz/projects/kosapi/wiki/Courses#GET-coursescodestudents
+      ##
+      # Example:
+      #   client.courses.find({course_code}).students
+      #   client.courses.find({course_code}).sem({semester_code}).students
+      ###
+      def students
+        raise 'Call #find before asking for students' unless id_set?
+        url_builder.set_path(id, 'students')
+        self
+      end
+
+      ###
+      # GET /courses/{code}/instances
+      #
+      # URI: https://kosapi.fit.cvut.cz/api/3/courses/{code}/instances/
+      # @link: https://kosapi.fit.cvut.cz/projects/kosapi/wiki/Courses#GET-coursescodeinstances
+      ##
+      # Example:
+      #   client.courses.find({course_code}).instances
+      ###
+      def instances
+        raise 'Call #find before asking for course instances' unless id_set?
+        url_builder.set_path(id, 'instances')
+        self
+      end
+
+      ###
+      # GET /courses/{code}/instances/{semester}
+      ###
+      def instance(semester)
+        raise 'Call #find before asking for course instance' unless id_set?
+        url_builder.set_path(id, 'instances', semester)
+        finalize
+      end
     end
   end
 end
diff --git a/spec/integration/courses_spec.rb b/spec/integration/courses_spec.rb
index c6b1cc9..afbfb16 100644
--- a/spec/integration/courses_spec.rb
+++ b/spec/integration/courses_spec.rb
@@ -25,4 +25,24 @@
     expect(page.items).to eq []
   end
 
+  describe "#parallels" do
+    it 'returns parallels for course in specified semester' do
+      parallels = client.courses.find('MI-PAA').sem('B141').parallels.limit(20)
+      expect(parallels.count).to eq 9
+    end
+  end
+
+  describe "#students" do
+    it 'returns students of course in specified semester' do
+      students = client.courses.find('MI-PAA').sem('B141').students.limit(200)
+      expect(students.count).to eq 188
+    end
+  end
+
+  describe "#instance" do
+    it 'returns instance for course in specified semester' do
+      instance = client.courses.find('MI-PAA').instance('B141')
+      expect(instance).to be_a KOSapiClient::Entity::Coursin
+    end
+  end
 end
diff --git a/spec/integration/parallels_spec.rb b/spec/integration/parallels_spec.rb
index 35117e4..db1f1dc 100644
--- a/spec/integration/parallels_spec.rb
+++ b/spec/integration/parallels_spec.rb
@@ -44,7 +44,7 @@
   end
 
   it 'parses timetable slot ID' do
-    page = client.parallels
+    page = client.parallels.query('course.code' => 'MI-PAA')
     slot = page.items.first.timetable_slots.first
     expect(slot.id).not_to be_nil
   end
diff --git a/spec/kosapi_client/entity/data_mappings_spec.rb b/spec/kosapi_client/entity/data_mappings_spec.rb
index 155cc40..835cd52 100644
--- a/spec/kosapi_client/entity/data_mappings_spec.rb
+++ b/spec/kosapi_client/entity/data_mappings_spec.rb
@@ -108,6 +108,14 @@
       expect(instance.foo).to eq '123'
     end
 
+    it 'supports array wrapping element name configuration' do
+      dummy_class.map_data :foo, String, array_wrapper_element: :bar
+      instance = dummy_class.parse(foo: {bar: ['123','456']})
+      expect(instance.foo).to be_a Array
+      expect(instance.foo.count).to eq 2
+      expect(instance.foo.first).to eq '123'
+    end
+
   end
 
   describe '#to_hash' do
diff --git a/spec/kosapi_client/resource/courses_builder_spec.rb b/spec/kosapi_client/resource/courses_builder_spec.rb
index b9de371..5535f0f 100644
--- a/spec/kosapi_client/resource/courses_builder_spec.rb
+++ b/spec/kosapi_client/resource/courses_builder_spec.rb
@@ -17,4 +17,77 @@
     end
 
   end
+
+  describe '#students' do
+
+    before { allow(url_builder).to receive(:set_path) }
+
+    it 'throws error when course id not set' do
+      expect { builder.students }.to raise_error(RuntimeError)
+    end
+
+    it 'returns self' do
+      builder.find(42)
+      expect(builder.students).to eq builder
+    end
+
+    it 'adds students to URL' do
+      expect(url_builder).to receive(:set_path).with(42, 'students')
+      builder.find(42).students
+    end
+  end
+
+  describe '#parallels' do
+
+    before { allow(url_builder).to receive(:set_path) }
+
+    it 'throws error when course id not set' do
+      expect { builder.parallels }.to raise_error(RuntimeError)
+    end
+
+    it 'returns self' do
+      builder.find(42)
+      expect(builder.parallels).to eq builder
+    end
+
+    it 'adds students to URL' do
+      expect(url_builder).to receive(:set_path).with(42, 'parallels')
+      builder.find(42).parallels
+    end
+  end
+
+  describe '#instances' do
+
+    before { allow(url_builder).to receive(:set_path) }
+
+    it 'throws error when course id not set' do
+      expect { builder.instances }.to raise_error(RuntimeError)
+    end
+
+    it 'returns self' do
+      builder.find(42)
+      expect(builder.instances).to eq builder
+    end
+
+    it 'adds instances to URL' do
+      expect(url_builder).to receive(:set_path).with(42, 'instances')
+      builder.find(42).instances
+    end
+  end
+
+  describe '#instance' do
+
+    before { allow(url_builder).to receive(:set_path) }
+
+    it 'throws error when course id not set' do
+      expect { builder.instance('foo') }.to raise_error(RuntimeError)
+    end
+
+    it 'adds instance to URL' do
+      expect(url_builder).to receive(:set_path).with(42)
+      expect(url_builder).to receive(:set_path).with(42, 'instances', 'foo')
+      builder.find(42).instance('foo')
+    end
+  end
+
 end