diff --git a/filtering.go b/filtering.go
index 82f5e4c..a56a4f9 100644
--- a/filtering.go
+++ b/filtering.go
@@ -7,20 +7,24 @@ import (
 	"strings"
 )
 
-type Filter map[string]string
+type Filter map[string][]string
 
-func (f *Filter) Size() int {
-	return len(*f)
+func (f Filter) Get(key string) (values []string, ok bool) {
+	values, ok = f[key]
+	return values, ok
 }
 
-func (f *Filter) Valid() bool {
-	return len(*f) > 0
+func (f Filter) Size() int {
+	return len(f)
+}
+
+func (f Filter) IsNotEmpty() bool {
+	return len(f) > 0
 }
 
 func (fs Filter) validate(validFilters []string) (Filter, bool) {
-	goodFilters := make(map[string]string)
-	cnt := 0
-	len := 0
+	goodFilters := make(Filter)
+	cnt, len := 0, 0
 	for f, _ := range fs {
 		len++
 		for _, v := range validFilters {
@@ -45,14 +49,19 @@ func ParseFilters(req *http.Request, header string) (filters Filter) {
 	q := req.FormValue(header)
 	q = strings.Trim(q, "\"")
 	kvp := strings.Split(q, "|")
-	filters = make(map[string]string, len(kvp))
+	filters = make(Filter, len(kvp))
 
 	for i, _ := range kvp {
 		kv := strings.Split(kvp[i], "::")
 		if len(kv) == 2 {
 			key, _ := url.QueryUnescape(kv[0])
-			val, _ := url.QueryUnescape(kv[1])
-			filters[key] = val
+
+			// get values (if more than 1)
+			vals := strings.Split(kv[1], ",")
+			for _, v := range vals {
+				u, _ := url.QueryUnescape(v)
+				filters[key] = append(filters[key], u)
+			}
 		}
 	}
 
@@ -64,30 +73,45 @@ func MakeFilterString(prefix string, filters Filter, validFilters []string) (res
 	if prefix != "" {
 		prefix += "."
 	}
-	if len(filters) == 0 {
+
+	if !filters.IsNotEmpty() {
 		return "", true
 	}
 
 	filters, ok = filters.validate(validFilters)
 	if !ok {
-		return "", ok
+		return "", false
 	}
 
-	symbol := "="
-	for k, v := range filters {
-		if res != "" {
+	for k, filter := range filters {
+		first := true
+		symbol := "="
+
+		if first {
 			res += " and "
+			first = false
 		} else {
 			res += " where "
 		}
-		c := string(v[0])
-		if c == "<" || c == ">" {
-			symbol = "" // examples: >3, >=3
-		} else {
-			symbol = "="
-		}
 
-		res += fmt.Sprintf("%s%s %s '%s'", prefix, k, symbol, v)
+		res += "("
+		for i, f := range filter {
+			if strings.HasPrefix(f, "<") || strings.HasPrefix(f, ">") {
+				symbol = string(f[0])
+				f = strings.TrimLeft(f, "<>")
+				if strings.HasPrefix(f, "=") {
+					f = strings.TrimLeft(f, "=")
+					symbol += "="
+				}
+			}
+
+			res += fmt.Sprintf("%s%s %s '%s'", prefix, k, symbol, f)
+
+			if i < len(filter)-1 {
+				res += " or "
+			}
+		}
+		res += ")"
 	}
 
 	return res, ok