ABSTRACT
If λ = 1, then the design is a (v;w1, w2;w3;K)-♦-IPBD. 1.42 Remark Completing an RBIBD(v −w1, k − 1, 1) having w1 parallel classes, and con-
taining an RBIBD(w2 −w3, k− 1, 1) subdesign having w3 parallel classes where each of the w3 parallel classes lies within one parallel class of the containing design provides one fruitful way of constructing a (completed) (v;w1, w2;w3; k, 1)−♦-IPBD.
