^{{Citation |first=Derek |last=Wall |title=The Rise of the Green Left: Inside the Worldwide Ecosocialist Movement |publisher=Pluto Press |year=2010 |page=97
^Populism Report Q3 2018(PDF). Foundation for European Progressive Studies. [27 March 2019]. (原始内容(PDF)存档于27 March 2019).
^Portugal's bright outlook offers Europe some hope. Financial Times. 25 August 2019. (原始内容存档于10 December 2022). The alliance between Mr Costa's Socialist Party (PS) and further left groups such as the anti-establishment Left Bloc was considered tenuous when it was forged in 2015. 含有連結內容需訂閱查看的頁面 (link)
Portugal - Political Parties - Elections. perspective.usherbrooke.ca. [11 May 2019]. (原始内容存档于2023-04-08) (法语).Portugal : la coalition de droite conserve le pouvoir. perspective.usherbrooke.ca. 26 October 2015 [11 May 2019]. (原始内容存档于2024-01-25) (法语). Deux autres partis de " gauche " étaient en lice pour les élections. Premièrement, le Bloc de gauche, considéré par le journal The Guardian comme étant une version portugaise du parti politique grec anti-austérité Syriza, a récolté 10,2% des suffrages (8).
Portugal, Le paysage politique. BiblioMonde. [2018-12-11]. (原始内容存档于2018-11-15) (法语). BE, le Bloc des gauches (Bloco da Esquerda) : formation regroupant l’extrême gauche portugaise depuis 1999. Influente dans les milieux intellectuels de la capitale, BE a obtenu 2,7% des voix et 3 députés en mars 2002 (soit un siège de plus qu’en 1999). BE comprend notamment l'Union démocratique populaire (União Democràtica Popular), le Parti socialiste révolutionnaire (Partido Socialista Revolucionario ) et Politica XXI..
Left Bloc (BE). The Democratic Society. 19 May 2014 [26 August 2018]. (原始内容存档于28 May 2019). The Left Bloc is the more socially libertarian, and bohemian of Portugal's two far-left structures.
Cunha, Carlos. Few but Pure and Good Members are Preferred to a Mass Party – The Portuguese Communist Party's Continued Orthodoxy. Communist and Post-Communist Parties in Europe. Hannah Arendt Institute Research on Totalitarianism. Vandenhoeck & Ruprecht. 2008 [16 March 2024]. ISBN 978-3525369128.
As Europe left struggles, Portugal's alliance wins over voters and Brussels. reuters.com. 31 March 2017 [11 May 2019]. (原始内容存档于2023-04-08) (英语). The unlikely alliance of center-left Socialists and two far-left parties has overcome deep scepticism since it was formed in 2015, achieving stability and maintaining economic recovery at a time of political uncertainty across Europe.