The classical phase of Indo-European comparative linguistics leads from Bopp to August Schleicher's 1861 "Compendium" and up to Karl Brugmann's 5-volume "Grundriss" (outline of Indo-European languages) published from 1886 to 1893. Brugmann's Neogrammarian re-evaluation of the field and Ferdinand de Saussure's proposal of the concept of "consonantal schwa" (which later evolved into the laryngeal theory) may be considered the beginning of "contemporary" Indo-European studies. The Indo-European proto-language as described in the early 1900s in its main aspects is still accepted today, and the work done in the 20th century has been cleaning up and systematizing, as well as the incorporation of new language material, notably the Anatolian and Tocharian branches unknown in the 19th century, into the Indo-European framework.