[1] He initially studied accounting at the Istituto Carlo Cattaneo in the city, before graduating with a degree in economics and commercial sciences at the University of Turin in 1924.

[2] Having long held ambitions to become a journalist, after serving with the Italian Army in the First World War he entered the editorial staff of the Milanese newspaper La Sera.

[2] In 1919 he formed the Aracne publishing house with his brother Attilio, and subsequently helped to establish an industrial co-operative that launched the first incarnation of the Milan Trade Fair.

[2] The PSU, having broken away from the Italian Socialist Party (PSI), was absorbed back into it in 1930, and Tremelloni emerged as a prominent member of its reformist wing, alongside the likes of Turati, Claudio Treves, Carlo Rosselli and Giuseppe Saragat.

[2] Having struggled to find an academic post due to his anti-fascist beliefs, in 1930 Tremelloni became a lecturer in political economy at the University of Geneva in Switzerland.

[4] Having escaped confinement for his anti-fascist activities, during the Second World War he maintained a low profile, retreating to the town of Cocquio-Trevisago in Varese to focus on his work with Aracne and to writing a history of contemporary Italian industry.