Prior to the breakup of the Socialist Federal Republic of Yugoslavia in the early 90s, Serbian and Croatian were considered to be one language referred to as either Serbocroatian or Croatoserbian (Srpskohrvatski, Hrvatosrpski). Now it is referred to by a number of names in the nation-states where it is spoken, including Serbian, Croatian, Bosnian, and Montenegrin. In the United States at the moment it is frequently referred to as Bosnian/Croatian/Serbian.
This project focused specifically on Serbian and Croatian. In the Novi Sad Agreement of 1954, one of the conclusions set forth by the linguists who met there was that there were two co-standard regional variants of Serbocroatian, based on the literary tradition of Zagreb and Belgrade. This project thus selected newspapers from these two cities, rather than from other cities or countries in which Bosnian/Croatian/Serbian is spoken.
Deciding what constitutes a markedly regional variant is at times a difficult task. Orthographic variation between the dialect spoken in Zagreb (ijekavian) and the dialect spoken in Belgrade (ekavian) follows systematic patterns and is easy to identify. There is very little regional variation in actual grammatical structures, which also makes it easy to identify the few constructions in which it occurs.
Identifying the lexical variants was the murkiest aspect of the mark-up, and Bosnian Croatian Serbian: a Grammar with Sociolinguistic Commentary was used as guide.