Dalam spektrum politik, sebuah ideologi, partai maupun posisi politik dapat diklasifikasikan dengan istilah kiri dan kanan. Sistem klasifikasi ini mempertentangkan politik sayap kiri dan sayap kanan.[1] Istilah ini berasal dari Prancis, dimana sayap kiri dianggap sebagai "partai gerakan" dan sayap kanan sebagai "partai keteraturan".[2][3][4][5] Posisi di tengah-tengah dua sayap ini disebut sentrisme atau posisi moderat.[1] Selain itu, pada kenyataannya seseorang atau suatu kelompok dapat saja memiliki posisi sayap kiri dalam suatu hal dan sayap kanan dalam hal lain.[6]
^Risen, Clay (2015). "The Bill of the Century", passim, e.g. "Southern Democrats faced three choices: they could ditch their party for the Republicans; move to the left and hope to ride a wave of an expanding post-Jim Crow black electorate; or double down on segregation and white supremacy ..." p. 168, Bloomsbury Press. ISBN978-1608198269
^Brooks, Frank H. (1994). The Individualist Anarchists: An Anthology of Liberty (1881–1908). Transaction Publishers. p. xi. "Usually considered to be an extreme left-wing ideology, anarchism has always included a significant strain of radical individualism ..."
Euclid Tsakalotis, "European Employment Policies: A New Social Democratic Model for Europe" in The Economics of the Third Way: Experiences from Around the World (eds. Philip Arestis & Malcolm C. Sawyer: Edward Elgar Publishing 2001), p. 26: "most left-wing approaches (social democratic, democratic socialist, and so on) to how the market economy works...").
"Introduction" in The Nordic Model of Social Democracy (eds. Nik Brandal, Øivind Bratberg & Dag Einar Thorsen: Palgrave Macmillan, 2013): "In Scandinavia, as in the rest of the world, 'social democracy' and 'democratic socialism' have often been used interchangeably to define the part of the left pursuing gradual reform through democratic means."
^Joanne C. Reuss, American Folk Music and Left-Wing Politics, The Scarecrow Press, 2000, ISBN978-0-8108-3684-6
^Van Gosse, The Movements of the New Left, 1950–1975: A Brief History with Documents, Palgrave Macmillan, 2005, ISBN978-1-4039-6804-3
^Michael J. Klarman, "From Jim Crow to Civil Rights: The Supreme Court and the Struggle for Racial Equality", "... many of the white Americans who were most sympathetic to racial equality belonged to left-wing organizations...", p. 375, Oxford University Press, 2006, ISBN978-0195310184
Heikki Paloheimo, "Between Liberalism and Corporatism: The Effect of Trade Unions and Governments on Economic Performance in Eighteen OECD Countries" in Labour Relations and Economic Performance: Proceedings of a Conference Held By the International Economic Association in Venice, Italy (eds. Renator Brunetta & Carlo Dell'Aringa: International Economic Association/Palgrave Macmillan, 1990), p. 119: "It is easier for trade unions to have mutual understanding with left-wing governments than with right-wing governments. In the same way, it is easier for left-wing governments to have mutual understanding with trade unions."
Thomas Poguntke, "Living in Separate Worlds? Left-wing Parties and Trade Uions in European Democracies" in Citizenship and Democracy in an Era of Crisis (eds. Thomas Poguntke et al.: Routledge: 2015), p. 173 ("So far we have argued that parties of the left are the natural allies of the trade union movement ... it goes almost without saying that this a simplification."), p. 181: "When it comes to overlapping memberships, left-wing parties have always been, by and large, strongly connected to the trade union movement.").
Politics in Europe, 6th ed. (eds. M. Donald Hancock et al.: SAGE/CQ Press, 2015), p. 139: "Historically, the political right was characterized by its identification with the status quo. It favored monarchism and deplored the Revolutions of 1789 and 1848."
Thomas M. Magstadt, Understanding Politics: Ideas, Institutions, and Issues, 12th ed. (Centgage Learning, 2015), p. 28: "Ideologies of the right: Monarchism is at the opposite end of the political spectrum .... After World War I, fascism supplanted monarchism as the principle ideology of the extreme Right."
Robert O. Paxton, The Anatomy of Fascism, passim, e.g. "The Communist International was certain that the German swing to the Right under Hitler would produce a counterswing to the Left ...", p. 128, Vintage, 2005, ISBN978-1400033911;
Hans-Georg Betz, Radical Right-Wing Populism in Western Europe (Macmillian, 1994), p. 23: "One of the central arguments in the literature on fascism was that fascism, and by extension all radical right-wing movements..."
The Concise Columbia Encyclopedia, Columbia University Press, ISBN0-231-05678-8 "Fascism, philosophy of government that glorifies nationalism at the expense of the individual. ... The term was first used by the party started by MUSSOLINI, ... and has also been applied to other right-wing movements such as NATIONAL SOCIALISM, in Germany, and the FRANCO regime, in Spain."
^Boswell, Jonathan (2013). Community and the Economy: The Theory of Public Co-operation (dalam bahasa Inggris). London; New York: Routledge. hlm. 160. ISBN978-1136159015.
^Aspinall, Edward; Fossati, Diego; Muhtadi, Burhanuddin; Warburton, Eve (24 April 2018). "Mapping the Indonesian political spectrum". New Mandala (dalam bahasa Inggris). Diarsipkan dari versi asli tanggal 30 January 2023. Diakses tanggal 13 February 2023.Parameter |url-status= yang tidak diketahui akan diabaikan (bantuan)