Given the wealth of scientific publications, perusing papers is becoming a larger and more complex burden, especially for junior researchers. In this work, we suggest a visualization-based method to mitigate this problem via the use of paper maps, i.e., concept maps for the summarization of scientific papers. We provide design principles of paper maps and discuss design considerations based on exploratory design studies. We also conducted an initial evaluation for assessing the effectiveness of paper maps in summarizing scientific papers, suggesting that paper maps can improve the readability of scientific papers.