“…Some relevant contributions on the subject are the works of Sarkar et al [12], Sen and Goyal [13], Holst [4], Dafnis et al [14], Huffer and Sethuraman [15], and Makri and Psillakis [16]. Applications of constrained ( , ℓ) strings of the general ( ≤ ≤ ℓ) or the restricted forms ( ≤ ℓ, = , ≥ ) were found in information theory and data compression (see Zehavi and Wolf [17], Jacquet and Szpankowski [18], and Stefanov and Szpankowski [19]) in urn models, record models, and random permutations (see Chern et al [20], Joffe et al [21], Chern and Hwang [22], Holst [5,9,10,23], and Huffer et al [24]) in system reliability (see Eryilmaz and Zuo [25], Eryilmaz and Yalcin [6], and Makri [26]) and in biomedical engineering (see Dafnis and Philippou [27]).…”