The researchers include five sources in their review of the literature that are a mixture of primary and secondary scholarly journals. The primary sources are articles of original research in peer-reviewed journals. The secondary sources take the form of review articles not based on original research but the research of others. Four of the journal articles used in the review of literature are primary sources. For example, Bostick and Wendelgass’ (1987) study on instillation of normal saline is original research published in a peer-reviewed journal. The study presented by Demers and Saklad (1973) is not a primary but rather a secondary source. This is because the study takes the form of a review article of research on techniques of tracheal aspiration conducted by others.
The sources used are current, considering the lag between the conclusion of research and publication in peer-reviewed journals. Most of the
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