This document outlines various clustering protocols for heterogeneous wireless sensor networks (HWSN). It begins by defining keywords related to HWSN and challenges in these networks, such as limited energy and heterogeneous hardware. The goals of clustering protocols are then discussed, including load balancing, fault tolerance and energy efficiency. Various clustering methods, attributes and models are classified. Examples of heterogeneous resources, impacts and performance measures are provided. The document also lists relevant conferences, simulators and laboratories, and provides author details.