2d - The import aurelienribon cannot be resolved

I've been having problems with using the Tween Engine by aurelien ribon for a Splash Screen for my 2d game. I'm using Eclipse and libgdx.

I've tried rebuilding, clean...-ing, and refreshing.

I've closely followed the import directions from here: https://github.com/libgdx/libgdx/wiki/Universal-Tween-Engine

I'd be more than happy to provide anyone with more information/code if they need it.

The import file/lines of code (Game Renderer class):

package com.companyname.gameWorld;

import aurelienribon.tweenengine.Tween;
import aurelienribon.tweenengine.TweenEquations;
import aurelienribon.tweenengine.TweenManager;

build.gradle:

project(":android") {

    apply plugin: "android"

    configurations { natives }

    dependencies {
        compile project(":core")
        compile "com.badlogicgames.gdx:gdx-backend-android:$gdxVersion"
        natives "com.badlogicgames.gdx:gdx-platform:$gdxVersion:natives-armeabi"
        natives "com.badlogicgames.gdx:gdx-platform:$gdxVersion:natives-armeabi-v7a"
        natives "com.badlogicgames.gdx:gdx-platform:$gdxVersion:natives-x86"

        compile "com.badlogicgames.gdx:gdx-box2d:$gdxVersion"
        natives "com.badlogicgames.gdx:gdx-box2d-platform:$gdxVersion:natives-armeabi"
        natives "com.badlogicgames.gdx:gdx-box2d-platform:$gdxVersion:natives-armeabi-v7a"
        natives "com.badlogicgames.gdx:gdx-box2d-platform:$gdxVersion:natives-x86"
        compile "com.badlogicgames.gdx:gdx-freetype:$gdxVersion"
        natives "com.badlogicgames.gdx:gdx-freetype-platform:$gdxVersion:natives-armeabi"
        natives "com.badlogicgames.gdx:gdx-freetype-platform:$gdxVersion:natives-armeabi-v7a"
        natives "com.badlogicgames.gdx:gdx-freetype-platform:$gdxVersion:natives-x86"

        compile "com.badlogicgames.gdx:gdx-bullet:$gdxVersion"

        natives "com.badlogicgames.gdx:gdx-bullet-platform:$gdxVersion:natives-armeabi"
        natives "com.badlogicgames.gdx:gdx-bullet-platform:$gdxVersion:natives-armeabi-v7a"
        natives "com.badlogicgames.gdx:gdx-bullet-platform:$gdxVersion:natives-x86"

        compile fileTree(dir: '../libs', include: '*.jar')
    }
}

...(other project(":...")s)...

project(":core") {

    apply plugin: "java"


    dependencies {
        compile "com.badlogicgames.gdx:gdx:$gdxVersion"
        compile "com.badlogicgames.gdx:gdx-box2d:$gdxVersion"
        compile "com.badlogicgames.gdx:gdx-freetype:$gdxVersion"

        compile "com.badlogicgames.gdx:gdx-bullet:$gdxVersion"


        compile fileTree(dir: '../libs', include: '*.jar')
    }
}

The /libs folder:

Answer

In the /libs folder, right click the two tween-engine.jar files, Build Path > Add to Build Path