“…Then, the full text of each work was carefully reviewed to eliminate those that were not related to the field of -optimization‖ or -scheduling‖. Finally, two hundred and forty-six publications including one hundred and seventy-nine journal articles , thirty-seven master and doctoral dissertations , twelve textbooks [224][225][226][227][228][229][230][231][232][233][234][235], and eighteen industrial reports [236][237][238][239][240][241][242][243][244][245][246][247][248][249][250][251][252][253] were selected for their relevance to the topic. Figure 3 represents a bar chart of number of publications concerning maintenance policy optimization and inspection planning of wind turbine systems in five-year periods, from 1997 to 2001, 2002 to 2006, 2007 to 2011, and 2012 As can be seen, over 72% of the publications have appeared during last five years which indicates the increasing importance of the maintenance optimization in wind energy industry.…”