APA

Environmental Defense Fund, Natural Resources Defense Council, Sierra Club, Union of Concerned Scientists U.S. Public Interest Research Group, Natural Resources Defense Council, Sierra Club & Union of Concerned Scientists U.S. Public Interest Research Group.GLOBAL WARMING: Early Warning Signs. : .

Chicago

Environmental Defense Fund, Natural Resources Defense Council, Sierra Club, Union of Concerned Scientists U.S. Public Interest Research Group, Natural Resources Defense Council, Sierra Club and Union of Concerned Scientists U.S. Public Interest Research Group.GLOBAL WARMING: Early Warning Signs. : .

Harvard

Environmental Defense Fund, Natural Resources Defense Council, Sierra Club, Union of Concerned Scientists U.S. Public Interest Research Group, Natural Resources Defense Council, Sierra Club and Union of Concerned Scientists U.S. Public Interest Research Group.GLOBAL WARMING: Early Warning Signs. : .

MLA

Environmental Defense Fund, Natural Resources Defense Council, Sierra Club, Union of Concerned Scientists U.S. Public Interest Research Group, Natural Resources Defense Council, Sierra Club and Union of Concerned Scientists U.S. Public Interest Research Group.: . .