1. On the nature of turbulence
2. On the failure of hyperbolicity in elasticity;Zak;J. Elasticity,1982
3. Postinstability in continuous systems, Parts I and II;Zak;Solid Mech. Arch.,1982
4. Postinstability in continuous systems, Parts I and II;Zak;Solid Mech. Arch.,1983
5. Wrinkling phenomenon in structures, Parts I and II;Zak;Solid Mech. Arch.,1983