Engineers use different types of information sources depending on the task in hand. Although technical information is one of the core information sources for engineers, engineering design projects also often require other types of sources in addition to technical ones.
For example, with respect to a project on transmission line sagging, the following is a list of several relevant sources of possible information sources.
AlcanCable- ACSR Data Product details and specifications
An investigation report by an energy expert A personal blog
HydroOne's Ontario Grid Control Centre (OGCC)
IEEE Standard 738-21012 IEEE Standards for Calculating the Current-Temperature of Bare Overhead Conductors
Report
These are but a few examples of related information sources in addition to journals, books, manuals, technical reports, etc.