function checkField() {

str1 = document.form.syear.value;
str2 = document.form.eyear.value;
if(str1 > str2 || (str1=='' ^ str2=='')) {
	document.form.syear.focus();
	alert("발행연도를 올바르게 입력하세요.");
	return;
}

str1 = document.form.s_ti.value;
str2 = document.form.s_au.value;
str3 = document.form.s_abs.value;
str4 = document.form.syear.value;

if(str1=='' && str2=='' && str3=='' && str4=='') {
	document.form.s_ti.focus();
	alert("검색조건을 입력하세요.");
	return;
}

document.form.action = "./result.php";
document.form.submit() ;
}