toplevel "A";
"A" wsp "I" "B";
"B" or "C" "J";
"C" or "K" "L";
"I" lambda=0.5 dorm=0;
"J" lambda=0.5 dorm=0;
"K" lambda=0.5 dorm=0;
"L" lambda=0.5 dorm=0;