In other areas, questionnaires were picked up by census enumerators. The census in 2002 involved some 50,000 enumerators and supervisors. The census enumerators were typically from the village or neighbourhood and often knew the residents. This was the last federal census conducted using the US Marshal Service as enumerators. For the remaining 20%, questionnaires were dropped off by enumerators. In CLU and C#, generators are called "iterators", and in Ruby, "enumerators". As part of a drive to increase the count's accuracy, 635,000 temporary enumerators were hired. Enumerators were instructed to no longer use the "Mulatto" classification. Other techniques assigned arbitrary values to strings containing the names of the enumerators. Some enumerators did not tally their results. Quasi-polynomials appear throughout much of combinatorics as the enumerators for various objects. However, these early estimates and the methods used have been criticized by later enumerators. The instructions provided to enumerators endorsed this practice. In Brazil, handheld devices were used by enumerators to locate residences on the ground. The main source of enumerators are from teachers and university students.