# Correspondence on A Simplified Method for Evaluating the Natural Frequencies and Corresponding Modal Shapes of Multistorey Frames by E.H. Roberts and R.H. Wood

*Professor F. W. Williams (M) (University of Wales Institute of Science and Technology): It is useful to note that Armstrong's notation enables the authors' method to be stated, much more concisely and simply, as an application of the familiar stiffness matrix method, as follows.*