diff --git a/MantleAPI/BUILD.bazel b/MantleAPI/BUILD.bazel
index e533abec4c1db71434c6c4ebe9edad9ef300620d..54b5d534ac46b3cfa452c404d6fcf197617294f1 100644
--- a/MantleAPI/BUILD.bazel
+++ b/MantleAPI/BUILD.bazel
@@ -19,6 +19,9 @@ cc_library(
     visibility = [
         "//visibility:public",
     ],
+    deps = [
+        "@units",
+    ],
 )
 
 cc_library(
diff --git a/MantleAPI/include/MantleAPI/Common/simulation_time.h b/MantleAPI/include/MantleAPI/Common/simulation_time.h
deleted file mode 100644
index 7fd924a26d69b4a1e9541d71c4b6f09c43035e9c..0000000000000000000000000000000000000000
--- a/MantleAPI/include/MantleAPI/Common/simulation_time.h
+++ /dev/null
@@ -1,29 +0,0 @@
-/*******************************************************************************
- * Copyright (c) 2021, Bayerische Motoren Werke Aktiengesellschaft (BMW AG)
- *
- * This program and the accompanying materials are made
- * available under the terms of the Eclipse Public License 2.0
- * which is available at https://www.eclipse.org/legal/epl-2.0/
- *
- * SPDX-License-Identifier: EPL-2.0
- *******************************************************************************/
-
-//-----------------------------------------------------------------------------
-/** @file  simulation_time.h */
-//-----------------------------------------------------------------------------
-
-#ifndef MANTLEAPI_COMMON_SIMULATION_TIME_H
-#define MANTLEAPI_COMMON_SIMULATION_TIME_H
-
-#include <MantleAPI/Common/time_utils.h>
-
-namespace mantle_api
-{
-struct SimulationTime
-{
-  Time current_sim_time{0};
-  Time last_delta_time{0};
-};
-
-}  // namespace mantle_api
-#endif  // MANTLEAPI_COMMON_SIMULATION_TIME_H
diff --git a/MantleAPI/include/MantleAPI/Execution/i_environment.h b/MantleAPI/include/MantleAPI/Execution/i_environment.h
index e9b08fc13f456be34214299a2b402632af0e3237..7c031c84bb08cdc637b9cb6b4e1bc1eb3cbe265c 100644
--- a/MantleAPI/include/MantleAPI/Execution/i_environment.h
+++ b/MantleAPI/include/MantleAPI/Execution/i_environment.h
@@ -15,7 +15,6 @@
 #ifndef MANTLEAPI_EXECUTION_IENVIRONMENT_H
 #define MANTLEAPI_EXECUTION_IENVIRONMENT_H
 
-#include <MantleAPI/Common/simulation_time.h>
 #include <MantleAPI/Common/time_utils.h>
 #include <MantleAPI/EnvironmentalConditions/road_condition.h>
 #include <MantleAPI/EnvironmentalConditions/weather.h>
@@ -77,7 +76,7 @@ public:
   virtual void SetDateTime(mantle_api::Time time) = 0;
   virtual mantle_api::Time GetDateTime() = 0;
 
-  /// @brief Time since start of simulation and delta time to previous step
+  /// @brief Time since start of simulation
   virtual mantle_api::Time GetSimulationTime() = 0;
 
   virtual void SetWeather(Weather weather) = 0;
diff --git a/MantleAPI/include/MantleAPI/Traffic/entity_properties.h b/MantleAPI/include/MantleAPI/Traffic/entity_properties.h
index 7d6ac794053780870cd6b1b9cb8ab6c1c879c311..0e591df5d25630eda003eddae8f23dfe3f350016 100644
--- a/MantleAPI/include/MantleAPI/Traffic/entity_properties.h
+++ b/MantleAPI/include/MantleAPI/Traffic/entity_properties.h
@@ -176,7 +176,7 @@ struct PedestrianProperties : public EntityProperties
 
 struct StaticObjectProperties : public EntityProperties
 {
-  units::length::meter_t upwards_shift{0.0};
+  units::length::meter_t z_placement_offset{0.0};
 };
 
 }  // namespace mantle_api
diff --git a/MantleAPI/test/MantleAPI/Test/test_utils.h b/MantleAPI/test/MantleAPI/Test/test_utils.h
index 6bb16d4e012247bdf680597d5633dbae64438fcd..c11fe9d4bb741a1eb4cf3264e4a9eb13dfa5b691 100644
--- a/MantleAPI/test/MantleAPI/Test/test_utils.h
+++ b/MantleAPI/test/MantleAPI/Test/test_utils.h
@@ -35,7 +35,7 @@ class MockConverter : public mantle_api::ICoordConverter
 public:
   MOCK_METHOD(mantle_api::Vec3<units::length::meter_t>, Convert, (mantle_api::Position position), (const override));
 
-  mantle_api::Position Convert(mantle_api::Vec3<units::length::meter_t> vec) const override
+  mantle_api::Position Convert(const mantle_api::Vec3<units::length::meter_t>& vec) const override
   {
     std::ignore = vec;
     return mantle_api::Position{};
@@ -270,13 +270,13 @@ public:
               CreateStaticObjectProxy,
               (const std::string& name, const mantle_api::StaticObjectProperties& properties), ());
 
-  mantle_api::IEntity& Get(const std::string& name) override
+  std::optional<std::reference_wrapper<IEntity>> Get(const std::string& name) override
   {
     std::ignore = name;
     return test_vehicle_;
   }
 
-  mantle_api::IEntity& Get(mantle_api::UniqueId id) override
+  std::optional<std::reference_wrapper<IEntity>> Get(mantle_api::UniqueId id) override
   {
     std::ignore = id;
     return test_vehicle_;
@@ -294,8 +294,9 @@ public:
   }
   void Delete(UniqueId id) override { std::ignore = id; }
 
-  //    const std::vector<mantle_api::IEntity>& GetEntities() const override { return <#initializer #>{}; }
-  //    std::vector<mantle_api::IEntity>& GetEntities() override { return <#initializer #>; }
+  void RegisterEntityCreatedCallback(const std::function<void(IEntity&)>& callback) override { std::ignore = callback; }
+  void RegisterEntityDeletedCallback(const std::function<void(const std::string&)>& callback) override { std::ignore = callback; }
+  void RegisterEntityDeletedCallback(const std::function<void(UniqueId)>& callback) override { std::ignore = callback; }
 
 private:
   MockVehicle test_vehicle_{};
diff --git a/MantleAPI/test/interface_test.cpp b/MantleAPI/test/interface_test.cpp
index 51bf3fdf915a4c76b9009566729b28dd7a95c698..67a5ecf66c2518305109c3b215de4b18905dab4e 100644
--- a/MantleAPI/test/interface_test.cpp
+++ b/MantleAPI/test/interface_test.cpp
@@ -17,7 +17,7 @@
 TEST(InterfaceTest, GivenTeleportAction_When_ThenHostVehicleIsPlaced)
 {
   mantle_api::Position inert_pos{};
-  inert_pos = mantle_api::OpenDrivePosition{{0, 0}, 0, 0};
+  inert_pos = mantle_api::OpenDrivePosition{{0, 0}, units::length::meter_t{0}, units::length::meter_t{0}};
   mantle_api::MockEnvironment env{};
   env.CreateMap("dummy_map_path", {});
 
diff --git a/README.md b/README.md
index e31998126c1aab953ecae282eaf7549f7ffb44a6..539914fb0af5a9e6ffdc7b1ec1de9d89c312fcee 100644
--- a/README.md
+++ b/README.md
@@ -4,3 +4,10 @@ A collection of interfaces for abstraction between a scenario engine and an envi
 It is intended to be usable with a wide variety of scenario description languages by implementing according scenario engines. 
 
 Remark: This is currently work in progress and no stable state is reached yet. 
+
+## Used libraries
+
+### Units
+License: MIT License
+URL: https://github.com/nholthaus/units
+Version: v2.3.1