Product-Weighted Lead Codes Revisited. - Seyoum Getu; Louis W. Shapiro; Wen-Jin Woan (J. Comb. Theory A, 1982)

The Riordan group. - Louis W. Shapiro; Seyoum Getu; Wen-Jin Woan; Leon C. Woodson (Discret. Appl. Math., 1991)

How to Guess a Generating Function. - Seyoum Getu; Louis W. Shapiro; Wen-Jin Woan; Leon C. Woodson (SIAM J. Discret. Math., 1992)