Design an App Mockup

We need a designer to design required slicing and mock up for one of our mobile app. The app is similar to a mini billing software solution. Before handing over the project we would like to see few samples of the design work done by the interested designers to get an idea and feel about their creativity and skill sets. In depth details about the app will be provided to the selected designer after finalizing financial terms and signing a Non Disclosure Agreement (NDA) for the project.