If you have a known article (like a seed article), you can easily find articles that are mentioned that article, and newer research that has cited the article.
In PubMed, choose Single Citation Search 
Then enter information about the article you have. Author, year, and Journal Title will be the most helpful.
Depending on the article, usually you will see a References section so that you can easily link to those articles.
Look for Cited to see the newer research that has cited your specific article.
You can easily limit to forms of literature that are more relevant to the type of information you want. Keep these definitions in mind. You can limit to specific types from the pane after you complete a search.
| Review | An article or book published after examination of published material on a subject. It may be comprehensive to various degrees and the time range of material scrutinized may be broad or narrow, but the reviews most often desired are reviews of the current literature. The textual material examined may be equally broad and can encompass, in medicine specifically, clinical material as well as experimental research or case reports. State-of-the-art reviews tend to address more current matters. A review of the literature must be differentiated from HISTORICAL ARTICLE on the same subject, but a review of historical literature is also within the scope of this publication type. |
| Systematic Review | A review of primary literature in health and health policy that attempts to identify, appraise, and synthesize all the empirical evidence that meets specified eligibility criteria to answer a given research question. Its conduct uses explicit methods aimed at minimizing bias in order to produce more reliable findings regarding the effects of interventions for prevention, treatment, and rehabilitation that can be used to inform decision making. |
| Meta-analysis | Works consisting of studies using a quantitative method of combining the results of independent studies (usually drawn from the published literature) and synthesizing summaries and conclusions which may be used to evaluate therapeutic effectiveness, plan new studies, etc. It is often an overview of clinical trials. It is usually called a meta-analysis by the author or sponsoring body and should be differentiated from reviews of literature. |
| Clinical Trial | A work that reports on the results of a clinical study in which participants are assigned to receive one or more interventions so that researchers can evaluate the interventions on biomedical or health-related outcomes. |
| Randomized Controlled Trial | A work that reports on a clinical trial that involves at least one test treatment and one control treatment, concurrent enrollment and follow-up of the test- and control-treated groups, and in which the treatments to be administered are selected by a random process, such as the use of a random-numbers table. |