The relative emission from chromospheres and coronae: dependence on spectral type and age by Linsky, JL, Wood, BE, Youngblood, A, Brown, A, Froning, CS, France, K, Buccino, AP, Cranmer, SR, Mauas, P, Miguel, Y, Pinada, JS, Rugheimer, S, Vieytes, M, Wheatley, PJ, Wilson, DJ